%\iffalse
%
% File dates.dtx
% Copyright (C) 1996, 1997 by Frank Bennett.  All rights reserved.
%
% IMPORTANT NOTICE:
% 
% You are not allowed to change this file.  You may however copy
% this file to a file with a different name and then change the
% copy if (a) you do not charge for the modified code, (b) you
% acknowledge the author(s) in the new file, if it
% is distributed to others, and (c) you attach these same
% conditions to the new file.
% 
% You are not allowed to distribute this file alone.  You are not
% allowed to take money for the distribution or use of this file
% (or a changed version) except for a nominal charge for copying
% etc.
% 
% You are allowed to distribute this file under the condition that
% it is distributed with all of its contents, intact.
% 
% For error reports, or offers to help make this a more powerful,
% friendlier, and altogether more thrilling package, please contact me on
% fb@soas.ac.uk
% 
%<style>\NeedsTeXFormat{LaTeX2e}[1995/06/01]
%<style>\ProvidesPackage{dates}
%<style>  [1998/01/17 17:12:39 3.1 Dates parsing support (Frank Bennett)]
%\fi
%
% \def\fileversion{3.1}
% \def\filedate{1998/01/17 17:12:39}
%
%\iffalse
%<*driver>
\documentclass{ltxdoc}
%\CodelineIndex
%\RecordChanges
%\EnableCrossrefs
\begin{document}
\OnlyDescription    % Comment out for implementation details
\DocInput{dates.dtx}
\end{document}
%</driver>
%\fi
%
% \changes{v1.0}{1996/12/10}{Initial version separated from calendar.dtx}
% \changes{v1.0}{1996/12/12}{Overhauled to provide error handling and
%   various other features}
% \changes{v1.0}{1996/12/14}{Adapted the plain \TeX{} code for the phases
%   of the moon and used it to set it up a function item in a list.  It works!}
% \changes{v1.0}{1996/12/14}{Tidied up some sloppiness in the handling of groups.
%   No active characters now appear in braced text, and functions no longer
%   require square braces.  Documentation updated to this effect.}
% \changes{v1.0}{1996/12/15}{Modified toXmac to allow no-frills ranges.}
% \changes{v1.1}{1996/12/21}{Added handler for multiple enditall's.}
% \changes{v1.1}{1996/12/27}{Minor bug fixes for final release with the
%  Calendar package.}
% \changes{v1.2}{1997/01/18}{Changed gdef of characters in capsdown to
% plain def, so that diacritics and maths will not be screwed up
% by calendar.  Capsdown state is fixed by xdef immediately
% before group enclosing the capsdown; definition is in force
% only just before and just after the high-speed read of the
% argument.}
% \changes{v1.2}{1997/01/18}{Fixed a bug that the above fix produced
%   in the handling of function definitions.}
% \changes{v1.3}{1997/02/17}{Added code to support recursive dates
%  falling on exactly the same day of the month in every month.
%  Perhaps such dates should be permitted to conditionally shift to a nearby
%  day in the event of a holiday.  Perhaps not.}
% \changes{v1.4}{1997/03/01}{Large number of variable made
%  global, to prevent consumption of \TeX{} save space during
%  large runs.  Task not yet complete, but hardiness much
%  improved.}
% \changes{v1.4}{1997/03/01}{Cleanup of documentation; cut out
%  all user-level instructions in favour of a cross-reference
%  to user-level packages.}
% \changes{v1.4}{1997/03/02}{Inserted fix for broken \texttt{othmac} support.}
% \changes{v1.5}{1997/03/06}{Added initialization \texttt{let} to
%   definition of \texttt{daymac} to fix a bug reported by Miroslav
%   Novak.}
% \changes{v1.5}{1997/03/06}{Fixed algorithm for ending subranges
%   in recursive entries --- was ending one day too soon always.}
% \changes{v1.6}{1997/05/19}{Added language option.  Initial language
%   support covers English and Japanese.}
% \changes{v1.6}{1997/05/20}{German support added.  Thanks due to
%   Christian Horn.}
% \changes {v1.7}{1997/06/10}{Removed Japanese option --- far too
%   cumbersome to maintain.}
% \changes{v1.8}{1997/10/18}{New public release of all styles
%  and modules incorporating global bug-fixes.}
% \changes{v1.9}{1997/10/24}{Eliminated the final (touch wood!)
%  cross-nested variable bug.  Should run find on small \TeX's now.}
% \changes{v1.10}{1997/10/25}{Eliminated need for bogus entries
%  to protect against reads past end of file. }
% \changes{v1.11}{1997/10/26}{Added support for anniversaries.}
%
%\iffalse
% Source tree moved under RCS
% ---------------------------
% dates.dtx,v
% Revision 3.1  1998/01/17 17:12:39  root
% Release code
%
% Revision 2.15  1998/01/17 06:10:58  root
% *** empty log message ***
%
% Revision 2.14  1998/01/17 04:54:44  root
% *** empty log message ***
%
% Revision 2.13  1998/01/16 11:41:21  root
% *** empty log message ***
%
% Revision 2.12  1998/01/16 11:39:57  root
% *** empty log message ***
%
% Revision 2.11  1998/01/16 11:18:23  root
% *** empty log message ***
%
% Revision 2.10  1998/01/16 11:00:58  root
% *** empty log message ***
%
% Revision 2.9  1998/01/16 09:26:26  root
% *** empty log message ***
%
% Revision 2.8  1998/01/16 09:03:04  root
% *** empty log message ***
%
% Revision 2.7  1998/01/15 23:34:12  root
% *** empty log message ***
%
% Revision 2.6  1998/01/15 23:30:14  root
% *** empty log message ***
%
% Revision 2.5  1998/01/15 21:42:28  root
% *** empty log message ***
%
% Revision 2.4  1998/01/15 21:38:26  root
% Trivial change.
%
% Revision 2.3  1998/01/15 21:35:30  root
% First shot at proper language support.
%
% Revision 2.2.1.1  1997/11/07 11:16:06  root
% Eliminated \@gobble from \dates@@@read@@function.
%
% Revision 2.2  1997/11/07 10:44:05  root
% Release code.
%
% Revision 2.1.1.22  1997/11/05 07:40:27  root
% Confirming a string of changes implementing multi-argument
% (aka multi-lingual) support.
%
% Revision 2.1.1.21  1997/11/05 07:37:09  root
% *** empty log message ***
%
% Revision 2.1.1.20  1997/11/05 07:35:42  root
% *** empty log message ***
%
% Revision 2.1.1.19  1997/11/05 07:19:49  root
% *** empty log message ***
%
% Revision 2.1.1.18  1997/11/05 07:14:39  root
% *** empty log message ***
%
% Revision 2.1.1.17  1997/11/05 07:06:09  root
% *** empty log message ***
%
% Revision 2.1.1.16  1997/11/05 06:55:18  root
% *** empty log message ***
%
% Revision 2.1.1.15  1997/11/05 06:46:48  root
% *** empty log message ***
%
% Revision 2.1.1.14  1997/11/05 06:44:42  root
% *** empty log message ***
%
% Revision 2.1.1.13  1997/11/05 06:43:27  root
% *** empty log message ***
%
% Revision 2.1.1.12  1997/11/05 06:41:21  root
% *** empty log message ***
%
% Revision 2.1.1.11  1997/11/05 06:37:42  root
% Backed off from adding new macro.  Trying nesting of
% \@ifnextnparchar.
%
% Revision 2.1.1.10  1997/11/05 06:29:43  root
% Added calls to new macro \@ififnextnparchar, to cope
% with possibility of bent brace without following square
% brace.
%
% Revision 2.1.1.9  1997/11/04 21:29:48  root
% Added prototype code for picking up extra entries
%
% Revision 2.1.1.8  1997/11/04 19:52:15  root
% Moved the assignment to \dates@date to the top of
% \dates@init@weekly.  Careless error.
%
% Revision 2.1.1.7  1997/11/04 14:57:40  root
% Fixed local assignments of \dates@date and \dates@catch
% accidentally included in patch code.
%
% Revision 2.1.1.6  1997/11/04 14:45:10  root
% Re-applied patches to cope with the common recursive entries,
% now that the code for "every other" has made it necessary to
% move the assignment to \dates@date out of the common code
% for recursive entries.
%
% Revision 2.1.1.5  1997/11/04 08:25:42  root
% Fixed silly typing error in fix just applied.
%
% Revision 2.1.1.4  1997/11/04 08:23:08  root
% Moved downcasing code directly into \dates@execute
%
% Revision 2.1.1.3  1997/11/04 07:39:27  root
% Added missing ` to \dates@downcase
%
% Revision 2.1.1.2  1997/11/04 07:33:08  root
% Eliminated \capsdown from the code, installed new routine
% based on character constants and \cs{ifcase}.
%
% Revision 2.1.1.1  1997/11/04 05:06:07  root
% Development branch
%
% Revision 2.1  1997/11/01 15:08:09  bennett
% Release code.
%
% Revision 1.17.0.8  1997/11/01 14:29:11  root
% *** empty log message ***
%
% Revision 1.17.0.7  1997/11/01 13:28:54  root
% Range limit trap suspended for the present; this needs careful
% consideration, so that the "freeze" declaration is not rendered
% useless or unpredictable.
%
% Revision 1.17.0.6  1997/11/01 12:50:18  root
% Alterations to recursion routines broke anniversaries.  Rewritten.
% Also added optional counter \dates@range@limit, which cuts off
% recursive entries to save processing time.
%
% Revision 1.17.0.5  1997/11/01 11:38:52  root
% Fixed obvious error in initialization routine before testing;
% if the pinpoint date is greater than the beginning of the
% subrange, we just use that as the starting point.
%
% Revision 1.17.0.4  1997/11/01 11:34:41  root
% First draft of new "every other week" function.  "Other"
% invokes a terminating macro that expects a pinpoint date.
% This is then used as the base for every-other-week jumps.
%
% Revision 1.17.0.3  1997/11/01 11:13:35  root
% Moved setting of \dates@date in recursive entries from the
% generic opener \dates@read@exit@recurse into each of the
% alternative recursive definitions.  This gives us better
% control; it allows us to use a pinpoint date as a starting date
% for recursive processing.
%
% Revision 1.17.0.2  1997/11/01 10:52:56  root
% Incorporated fix for encounters with \end; we no longer
% need to gobble anything after the parsed text.
%
% Revision 1.17.0.1  1997/11/01 06:39:29  root
% Cut enditalls.
%
% Revision 1.17  1997/11/01 06:29:27  root
% New revision branch established to play with the elimination
% of \enditall's from the code.
%
% Revision 1.16  1997/10/31 21:28:07  root
% *** empty log message ***
%
% Revision 1.15  1997/10/31 21:13:53  root
% *** empty log message ***
%
% Revision 1.14  1997/10/31 20:47:16  root
% Moved date-validation code from \dates@fix to
% \dates@read@exit@default where it belongs.
%
% Revision 1.13  1997/10/31 19:35:20  root
% Eliminated \message's used to trace the problem with the
% streamlined date conversion code just introduced.
%
% Revision 1.12  1997/10/31 19:32:42  root
% Fixed egregious bug involving the use of \dates@day for two
% completely unrelated purposes.  With this fix, the more
% streamlined use of but one invocation of either \caldate or
% \dates@fix works.
%
% Revision 1.11  1997/10/31 18:51:19  root
% *** empty log message ***
%
% Revision 1.10  1997/10/31 18:29:43  root
% Eliminated what appeared to be unnecessary use of
% \dates@monthnameget from previous revision.  Caused an error,
% but this may not have been the source of that error.
%
% Revision 1.9  1997/10/31 18:23:06  root
% Added \dates@getmonthname and \dates@getdayname to the definition
% of \dates@fix.  This eliminates the need for running \caldate
% after \dates@fix, and will further reduce the processing burden.
%
% Revision 1.8  1997/10/31 18:01:23  root
% Finalized changes eliminating one use of \dates@capsdown.
% Also made further changes to documentation, and added
% (or rather changed) the name of \dates@@@@read@function
% and the following macro to \dates@@@read... to help make
% things a little easier to follow.
%
% Revision 1.7  1997/10/31 17:39:05  root
% Restored use of @default prefix for \dates@read.  Also
% trying the elimination of one instance of \dates@capsdown.
% If this works, it will eliminate a great deal of clutter
% in save space.
%
% Revision 1.6  1997/10/31 11:18:55  root
% Further documentation updates and what I thought were trivial
% changes to the code.  The trivial changes seem, however, to
% have broken the "list" declaration.
%
% Revision 1.5  1997/10/31 09:00:27  root
% First phase of combing through documentation.
%
% Revision 1.4  1997/10/29 20:08:04  bennett
% *** empty log message ***
%
% Revision 1.3  1997/10/29 13:50:13  root
% Restored use of date checking, after discovering that it
% works correctly if files are extracted using the -kv
% option.
%
% Revision 1.2  1997/10/29 11:47:37  root
% Eliminated optional date specification from RequirePackage{overword}
%
% Revision 1.1  1997/10/29 08:17:52  root
% Initial revision
%
%\fi
%
% \DoNotIndex{\@,\@@par,\@beginparpenalty,\@empty}
% \DoNotIndex{\@flushglue,\@gobble,\@input}
% \DoNotIndex{\@makefnmark,\@makeother,\@maketitle}
% \DoNotIndex{\@namedef,\@ne,\@spaces,\@tempa}
% \DoNotIndex{\@tempb,\@tempswafalse,\@tempswatrue}
% \DoNotIndex{\@thanks,\@thefnmark,\@topnum}
% \DoNotIndex{\@@,\@elt,\@forloop,\@fortmp,\@gtempa,\@totalleftmargin}
% \DoNotIndex{\",\/,\@ifundefined,\@nil,\@verbatim,\@vobeyspaces}
% \DoNotIndex{\|,\~,\ ,\active,\advance,\aftergroup,\begingroup,\bgroup}
% \DoNotIndex{\cal,\csname,\def,\documentstyle,\dospecials,\edef}
% \DoNotIndex{\egroup}
% \DoNotIndex{\else,\endcsname,\endgroup,\endinput,\endtrivlist}
% \DoNotIndex{\expandafter,\fi,\fnsymbol,\futurelet,\gdef,\global}
% \DoNotIndex{\hbox,\hss,\if,\if@inlabel,\if@tempswa,\if@twocolumn}
% \DoNotIndex{\ifcase}
% \DoNotIndex{\ifcat,\iffalse,\ifx,\ignorespaces,\index,\input,\item}
% \DoNotIndex{\jobname,\kern,\leavevmode,\leftskip,\let,\llap,\lower}
% \DoNotIndex{\m@ne,\next,\newpage,\nobreak,\noexpand,\nonfrenchspacing}
% \DoNotIndex{\obeylines,\or,\protect,\raggedleft,\rightskip,\rm,\sc}
% \DoNotIndex{\setbox,\setcounter,\small,\space,\string,\strut}
% \DoNotIndex{\strutbox}
% \DoNotIndex{\thefootnote,\thispagestyle,\topmargin,\trivlist,\tt}
% \DoNotIndex{\twocolumn,\typeout,\vss,\vtop,\xdef,\z@}
% \DoNotIndex{\,,\@bsphack,\@esphack,\@noligs,\@vobeyspaces,\@xverbatim}
% \DoNotIndex{\catcode,\end,\escapechar,\frenchspacing,\glossary}
% \DoNotIndex{\hangindent,\hfil,\hfill,\hskip,\hspace,\ht,\it,\langle}
% \DoNotIndex{\leaders,\long,\makelabel,\marginpar,\markboth,\mathcode}
% \DoNotIndex{\mathsurround,\mbox,\newcount,\newdimen,\newskip}
% \DoNotIndex{\nopagebreak}
% \DoNotIndex{\parfillskip,\parindent,\parskip,\penalty,\raise,\rangle}
% \DoNotIndex{\section,\setlength,\TeX,\topsep,\underline,\unskip,\verb}
% \DoNotIndex{\vskip,\vspace,\widetilde,\\,\%,\@date,\@defpar}
% \DoNotIndex{\[,\{,\},\]}
% \DoNotIndex{\count@,\ifnum,\loop,\today,\uppercase,\uccode}
% \DoNotIndex{\baselineskip,\begin,\tw@}
% \DoNotIndex{\a,\b,\c,\d,\e,\f,\g,\h,\i,\j,\k,\l,\m,\n,\o,\p,\q}
% \DoNotIndex{\r,\s,\t,\u,\v,\w,\x,\y,\z,\A,\B,\C,\D,\E,\F,\G,\H}
% \DoNotIndex{\I,\J,\K,\L,\M,\N,\O,\P,\Q,\R,\S,\T,\U,\V,\W,\X,\Y,\Z}
% \DoNotIndex{\1,\2,\3,\4,\5,\6,\7,\8,\9,\0}
% \DoNotIndex{\!,\#,\$,\&,\',\(,\),\+,\.,\:,\;,\<,\=,\>,\?,\_}
% \DoNotIndex{\discretionary,\immediate,\makeatletter,\makeatother}
% \DoNotIndex{\meaning,\newenvironment,\par,\relax,\renewenvironment}
% \DoNotIndex{\repeat,\scriptsize,\selectfont,\the,\undefined}
% \DoNotIndex{\arabic,\do,\makeindex,\null,\number,\show,\write,\@ehc}
% \DoNotIndex{\@author,\@ehc,\@ifstar,\@sanitize,\@title,\everypar}
% \DoNotIndex{\if@minipage,\if@restonecol,\ifeof,\ifmmode}
% \DoNotIndex{\lccode,\newtoks,\onecolumn,\openin,\p@,\SelfDocumenting}
% \DoNotIndex{\settowidth,\@resetonecoltrue,\@resetonecolfalse,\bf}
% \DoNotIndex{\clearpage,\closein,\lowercase,\@inlabelfalse}
% \DoNotIndex{\selectfont,\mathcode,\newmathalphabet,\rmdefault}
% \DoNotIndex{\bfdefault}
%
% \title{User's Guide to the Dates package\thanks{This file is version number
%    \fileversion{}.  It was last revised on
%    \filedate.}}
%
% \author{Frank G. Bennett, Jr.\thanks{The code contained in this file just
%    provides a smart \LaTeXe front end to
%    the \texttt{calendar} macros for \TeX{} that I
%    found on CTAN.  The \TeX{} macros work quite
%    well, but lack any documentation.  Their provenance is also a
%    mystery.  If anyone can tell me who wrote them, I will gladly
%    include an acknowledgement in this documentation.}}
%
%  \maketitle
%
% \setcounter{StandardModuleDepth}{1}
% \DeleteShortVerb{\|}
% \MakeShortVerb{\"}
%
% \begin{abstract}
% \noindent This package provides macros for the parsing of dates
%  using \LaTeXe{}.
% \end{abstract}
%
% \CheckSum{1916}
%
% \section{Introduction}
%
% This package provides a macro, "\dateread", that can
% be used to parse date strings, either individually
% or recursively. The macro expects a human-readable
% syntax, which it converts into an integer (a ``long
% date'') that can
% be more easily used for some types of computation.
% A set of companion macros and token registers
% is also provided for
% converting long dates into human-readable form.
%
% Dates may be specified either individually,
% or as recursive dates within a range.
% The human-readable syntax for two
% types of recursive date are built
% into the package, but an interface for writing
% specialized extensions in native \LaTeX{} is also provided.
% The handling of parsed dates is also within
% user control; it is defined in a
% single argument fed to "\dateread" when it is invoked
% in front of a list of dates.
%
% This package was
% developed as one of the building blocks of
% the "calendar" package, but is released as a separate
% chunk of code because the date parsing task is a function
% discrete from the work of building a calendar from
% constituent blocks of information (which is the
% main task of the Calendar package proper).
%
% For a description of the syntax understood by
% the parser, and examples of how it can be
% extended, please see the Calendar package and
% the documentation for its associated style
% files.  The documentation here is not intended
% for end users; it is provided for reference by
% style designers who might wish to use
% the parser in their own packages.
%
% \section{Calling the Parser}
%
% Printing of
% variable text (such as the text of the date) is
% done by passing that information through to the argument
% to the "\dateread" macro.
% This argument is an action that will be performed
% once after each date in the list is read.  The
% date and the description text may be included by
% using the appropriate commands.  These are:
%
% \begin{tabular}{ll}
% "\theyear" & The year (four digits).\\
% "\themonth" & The full name of the month.\\
% "\theshortmonth" & The name of the month (3 characters).\\
% "\themonthnumber" & The number of the month.\\
% "\theday" & The day of the month.\\
% "\thetimestart" & Starting time for an item.\\
% "\thetimeend" & Ending time for an item.\\
% "\theweekday" & The name of the day of the week.\\
% "\theshortweekday" & Abbreviated day of the week (3 characters).\\
% "\theshorttext" & The text describing the date.\\
% "\thelongtext" & A longer description of the date.\\
% "\thelongdate" & The long date (an integer).\\
% "\thedays" & The maximum number of days this month.\\
% \end{tabular}
%
% You can also call up information using lower-level
% registers and macros that contain date-related
% information.  If you need to do this, you're
% on your own; please have a look at the code.
%
% The demonstration file included in this package
% lists dates on the terminal using the "\message"
% command.  In a more serious application, text can
% be printed, stored to registers or boxes, or
% sent in pre-processed form to an external file.
%
% The following is a valid invocation of the
% macro:
%
% \begin{quote}
% \begin{verbatim}
% \dateread{%
%   \message{%
%     \theweekday, %
%     \theday\space%
%     \themonthname\space%
%     \theyear}}
% %
% % The list of dates to be parsed
% %
% June 15 1997 {Summer Holiday Begins}
% September 25 1997 {Summer Holiday Ends}
% January 1 1997 {First day of January}
% February 18 1997 {Frank's Birthday}
% Every Monday at 2:00 {Go to the Beach}
% Every 20 {20th day of the month}
% %
% % The end of the list.
% %
% \relax{}
% \end{verbatim}
% \end{quote}
%
% A style package that uses the date parser
% should of course conceal stretches of code
% like that above from the end user.  If lists
% of dates are maintained in separate files, you
% can do something like the following,
%
% \begin{quote}
% \begin{verbatim}
% \def\readinput{%
%   \dateread{\message{\theweekday^^J}}}
%
% \def\inputandread{%
%   \expandafter\readinput%
%     \@@input \filename\relax{}
%   }
% \end{verbatim}
% \end{quote}
%
% \noindent where "\filename" contains the name of a file
% to be read.  One would confirm the existence
% of the file, then run "\inputandread".
%
% \section{Extending the Parser}
%
% \label{analyze}
% When the parser is used in a package, it may be
% necessary to modify its behaviour to perform
% special actions in the course of processing.
% For example, you may want to provide a facility
% for setting the range in files containing
% recursive dates from a single file so that,
% say, an academic schedule can be moved forward
% to the next year without a lot of typing.
% This kind of effect can be achieved by defining a
% word which diverts processing to a macro that
% performs the desired action before continuing
% to digest the list of dates.
%
% The flow of processing can be diverted at two
% points:
%
% \begin{enumerate}
% \item Immediately after a word is read;
% or
% \item Immediately after a date and its
% text have been digested.
% \end{enumerate}
%
% The parser can be
% re-entered in any of three states:
%
% \begin{enumerate}
% \item One that
% looks for the next word in a date string; 
% \item One that digests the description text; or
% \item One
% that completes the processing of a date
% entry and its text.
% \end{enumerate}
%
% Each of the exit points and reentry states is
% associated with a macro name.  Diversion is
% accomplished by defining a word that "\let"s the
% exit macro name be the user's own macro.  Reentry
% is accomplished in the user's macro by ending
% with the appropriate macro name.  The names
% the macros to use as exit points are,
% in the order of the first list above:
%
% \begin{enumerate}
% \item "\dates@@@read"
% \item "\dates@read@exit"
% \end{enumerate}
%
% The names of macros to use for reentry
% states are:
%
% \begin{enumerate}
% \item "\dates@@@read@default"
% \item "\dates@@@@read@default"
% \item "\dates@read@exit@default"
% \end{enumerate}
%
% An extension therefore consists of a user-defined
% macro, and a user-defined word that invokes
% "\let" as appropriate.  Words should be padded
% to exactly three characters using "X", and should
% be appended with the suffix "mac".  The following
% defines a word, "if", which sets a toggle and
% continues parsing a date:
%
% \begin{quote}
% \begin{verbatim}
% \newif\ifusedif
%
% \def\myownmacro{%
%   \usediftrue%
%   \dates@@@read@default}
%
% \def\ifXmac{%
%   \let\dates@@@read=\myownmacro}
% \end{verbatim}
% \end{quote}
%
% This is the same method used in the package
% itself to provide recursive dates and the
% function entry type; see the code commentary section
% for less trivial examples.
%
% \subsection{Using the Argument Text}
%
% When dates are read they are unsorted, so text should not
% be exported directly by \cs{dates@action} (let alone
% dropped on DVI)
% unless you have a filter for sorting
% the text after \TeX{} exits.  In normal use,
% events should be sorted and selected
% in memory after they are read, by other code in the
% package calling "dates.sty".  The Calendar package
% is an example of how this can be done.
%
%\StopEventually{\PrintIndex}
%
% \section{The Macros}
%
%    \begin{macrocode}
%<*style>
\newcount\dates@one
\newcount\dates@two
\newcount\dates@langnum
\newtoks\dates@reg@a
\newtoks\dates@reg@b
\newtoks\dates@reg@c
\def\DeclareCalendarLanguage#1#2#3#4#5{
  \advance\dates@two by1\relax%
  \expandafter\edef\csname dates@#1@langnum\endcsname{\the\dates@two}%
  \ifnum\dates@two=1\relax\def\dates@default@language{#1}\fi%
  \DeclareOption{#1}{%
    \expandafter\expandafter\expandafter%
      \dates@langnum\csname dates@#1@langnum\endcsname\relax%
    \dates@buildcase{1}{\theweekday}{\dates@weekd}#2{}%
    \dates@buildcase{1}{\theshortweekday}{\dates@weekd}#3{}%
    \dates@buildcase{0}{\themonth}{\dates@month}#4{}%
    \dates@buildcase{0}{\theshortmonth}{\dates@month}#5{}}}
\def\dates@buildcase#1#2#3{%
  \dates@one=#1\relax%
  \dates@reg@c={#3}%
  \gdef\dates@temp@a{#2}%
  \dates@reg@a={}%
  \dates@reg@b={}%
  \def\dates@temp@c{}%
  \dates@@buildcase}
\def\dates@@buildcase#1{%
  \ifcat$#1$%
    \let\next\dates@@@buildcase%
  \else%
    \let\next\dates@@buildcase%
    \dates@reg@a={\or#1}%
    \dates@reg@b=\expandafter{\dates@temp@c}%
    \edef\dates@temp@c{\the\dates@reg@b\the\dates@reg@a}
  \fi%
  \next}
\def\dates@@@buildcase{%
  \ifnum\dates@one=0\relax%
    \dates@reg@a=\expandafter{\dates@temp@c}%
  \else%
    \dates@reg@a=\expandafter\expandafter\expandafter%
      {\expandafter\@gobble\dates@temp@c}%
  \fi%
  \expandafter\edef\dates@temp@a{%
    \noexpand\ifcase\the\dates@reg@c%
    \the\dates@reg@a%
    \noexpand\fi}}
%    \end{macrocode}
% Load some useful code.
%    \begin{macrocode}
\RequirePackage{overword}[1997/10/29]
\InputIfFileExists{dates.cfg}{}{}
\@ifundefined{theweekday}{%
  \DeclareCalendarLanguage{english}
   {{Sun}{Mon}{Tue}{Wed}{Thu}{Fri}{Sat}}
   {{Sunday}{Monday}{Tuesday}{Wednesday}{Thursday}{Friday}{Saturday}}
   {{Jan}{Feb}{Mar}{Apr}{May}{Jun}{Jul}{Aug}{Sep}{Oct}{Nov}{Dec}}
   {{January}{February}{March}{April}{May}{June}{July}{August}{September}
    {October}{November}{December}}}
  {}
\ExecuteOptions{\dates@default@language}
\ProcessOptions
%    \end{macrocode}
%
% \subsection{The Engine Core}
%
% \begin{macro}{\dateread}
% The top-level interface macro \cs{dateread} starts by setting "\dates@action"
% to be its first argument.  It then initializes
% variables that are zeroed only at the start of a run
% of dates, and passes control to the next macro in the chain,
% \cs{dates@read}.
%    \begin{macrocode}
\long\gdef\dateread#1{%
  \gdef\dates@action{#1}%
  \gdef\dates@subranges{}%
  \dates@subrange@start=0%
  \dates@subrange@end=0%
  \dates@read@default}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\date@read}
% The next macro continues with initialization, 
% zeroing and blanking variables that need to
% be reset each time a new date is read.  The reason
% for the \texttt{@default} extension is explained below.
%    \begin{macrocode}
\long\gdef\dates@read@default{%
  \global\dates@time@start=0%
  \global\dates@time@end=0%
  \setyear{1900}%
  \global\dates@month=0%
  \global\dates@day=0%
  \global\dates@weekd@target=7%
  \gdef\theshorttext{}%
  \gdef\thelongtext{}%
%    \end{macrocode}
% \textit{The action, whatever the user has chosen it to be,
% can be suppressed by toggling the following condition,
% but the default here (as in life) is to do things.}
%    \begin{macrocode}
  \global\dates@suppressfalse%
%    \end{macrocode}
% \textit{Recursive entries will define the following two macros,
% but initially we want them to be firmly turned off.}
%    \begin{macrocode}
  \global\let\dates@init\relax%
  \global\let\dates@increment\relax%
%    \end{macrocode}
% \textit{The following assignments put the parsing machinery
% into its default state.  The first and the third macros below
% have \texttt{@default} values not to allow modification of
% parsing behaviour at these points, but because these two
% macros are \cs{relax}ed to bring parsing to a halt when
% desired.}
%    \begin{macrocode}
  \global\let\dates@read=\dates@read@default%
  \global\let\dates@@@read=\dates@@@read@default%
  \global\let\dates@@@@read=\dates@@@@read@default%
  \global\let\dates@read@exit=\dates@read@exit@default%
%    \end{macrocode}
% \textit{We open a group, and make uppercase characters active
% locally inside it.  We use an invocation of \cs{@ifnextnparchar} 
% to look for the next character.  If that is \cs{end},
% then we close the group we've just opened, and that's
% that.  This sudden-death condition will seldom be satisfied
% (you would need an \cs{end} immediately after \cs{dateread}
% with no intervening date, or a date complete with braced
% argument(s) followed immediately by \cs{end}), but the condition will
% be trapped and handled if it does occur.}  
%
% \textit{Apart from this, we look for a match to \cs{dates@serious@brace}.
% It will be spotted in most cases
% by the last invocation of \cs{@ifoverword} in parsing the
% date (re which see below).  The only case in which it will
% need to be caught here is where there is no date at all,
% but an immediate curly brace.}
%
% \textit{Thus, we will almost always be proceeding
% on the middle, ``fail'' condition to the next macro in
% the parsing chain, \cs{dates@@read}.}
%
% \textit{Apart from
% handling possible if slightly weird error conditions, this
% look forward will close a file, if one has been opened
% to provide the list read by \cs{dateread} (see \texttt{calendar.dtx},
% again, for a real-world example) and its text content has
% been exhausted.}
%    \begin{macrocode}
  \bgroup%
    \@ifnextnparchar\dates@serious@brace%
     {\message{This should never happen}}%
     {\dates@@read}%
     {\egroup}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\date@@read}
% We grab everything up to the next brace.  This
% will ordinarily be a single date, but it could be a
% range as well.  The text for parsing is \cs{xdef}ed,
% after first \cs{let}ting \cs{end} \cs{relax}.
% The \cs{relax}ed \cs{end} will expand to itself
% (I think they call this a ``quark''?) when \cs{xdef}ed.
% Then we end the current group, which
% will restore the definition
% of \cs{end}, whatever it may happen to be.
%
% We then place a space after the argument text to be
% sure we have one there, and
% run the next macro, \cs{dates@@@read}, in front of
% it.
%    \begin{macrocode}
\long\def\dates@@read#1#{%
    \let\end\relax%
    \xdef\cal@temp{#1 }%
  \egroup%
  \expandafter\dates@@@read\cal@temp}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\date@@@read}
% The \cs{dates@@@read@default} macro recursively
% picks through the argument text word by word
% using the \cs{@ifoverword} macro provided by the
% \texttt{overword} package.  Through the subsequent macro
% "\dates@analyze", the definitions of
% "\dates@@@read" and of "\dates@read@exit"
% may be altered to achieve special effects.  Any hooks that
% redefine these functions should chain to
% their default definitions.
%
% The \cs{@ifoverword} macro looks for \cs{dates@serious@brace}
% that we just placed after the scanned date string
% between us and the curly brace.
%
% This is one
% of several macros in the parsing chain that can
% be replaced with an alternative definition to
% accomplish special effects.
% In this code, the default
% definitions of such macros bear the root name with
% suffix "@default".  Special definitions bear the root name
% with a descriptive suffix.
%    \begin{macrocode}
\def\dates@@@read@default{%
%    \end{macrocode}
% \textit{If this macro has been called, we carefully be
% sure it's set as the default under the root name too.} 
%    \begin{macrocode}
    \global\let\dates@@@read\dates@@@read@default%
    \@ifoverword\dates@serious@brace%
%    \end{macrocode}
% \textit{If there is a match, we're at the end of the
% string.  We send the word we've collected to \cs{dates@analyze},
% and chain to the next
% processing macro, \cs{dates@@@@read}, when it exits.}
%    \begin{macrocode}
      {\expandafter\dates@analyze\@overword{}%
       \dates@@@@read}%
%    \end{macrocode}
% \textit{If the next token after the word we have just absorbed
% is not a brace (and not \cs{end}), then we send the
% absorbed word to \cs{dates@analyze} and reinvoke the
% current macro.}
%    \begin{macrocode}
      {\expandafter\dates@analyze\@overword{}%
       \dates@@@read}%
%    \end{macrocode}
% \textit{If we have hit \cs{end}, we want to recover gracefully,
% completing our work before expiring so that the \cs{end}
% can take effect.}
%
% \textit{The first thing we do is send the absorbed word to
% \cs{dates@analyze}.  Then we invoke \cs{dates@read@exit} to
% process the date (calculating the long date, and performing
% the action specified in the argument to \cs{dateread}) ---
% after first relaxing \cs{dates@read}, so that the
% \cs{dates@read@exit} macro will occur only once.}
%    \begin{macrocode}
      {\expandafter\dates@analyze\@overword{}%
       \ifnum\dates@year>0\relax%
         \let\dates@read\relax%
         \dates@read@exit%
       \fi}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\dates@@@@read}
% The following will read arguments (one mandatory
% argument in curly braces, one optional one in square
% braces) and save them for
% use as text descriptions applying to the date.  
% After the arguments are stored, we
% chain to the exit routine that will perform the action
% that the user gave to "\dateread".
%
% The macro is defined with a \texttt{@default} suffix,
% not because alternative processing is to be spliced in here,
% but because one method of ending recursive parsing
% is to \cs{let} this macro \cs{relax}.
%
% The effect we want to accomplish is to allow
% users to put any legal text, including square
% braces, inside \textrm{either} the curly braces marking
% the mandatory argument, \textrm{or} the square braces
% marking the optional argument.  The usual \LaTeX{} method
% of doing this, looking for a common or garden square brace
% with \cs{@ifnextchar} and then chaining to a
% macro that uses square braces as delimiters,
% will not accomplish this purpose; with that approach, 
% \textrm{any} square brace, regardless of nesting level,
% will end the argument.
%
% We need instead to see square braces as grouping characters.
% This will make them disappear when the text is expanded, but
% at least things won't blow up.
%
% To get ready for the optional argument (which comes \textrm{after}
% this macro), we set the open square brace to be a grouping
% character like "{".  We can't use this directly as an argument
% (because \TeX{} will try to keep reading
% text until it finds the matching brace), so we \cs{let}
% a macro have this token's value.  The \cs{let} is
% global because the value of "{" is global.
% Then we use the funny brace macro inside the
% definition as a match text for a square brace.  This
% works because the \cs{@ifnextnparchar} macro also works
% with \cs{let} (well, \cs{futurelet}, which amounts to the
% same thing in this context), resulting in an internal
% ``funny brace'' macro used for the comparison.
% All of this jiggery-pokery is necessary because
% the "\futurelet" command (used by "\@ifnextnparchar") will stamp
% a category code on the brace when it sees it, even though
% \TeX{} won't yet read the character itself in for processing.
%    \begin{macrocode}
\bgroup
  \catcode`\[=1
  \global\let\dates@funny@brace=[
  \catcode`\<=1
  \global\let\dates@bent@brace=<
\egroup
\gdef\dates@@@@read@default#1{%
%    \end{macrocode}
% We reset any alternative definitions that are accidentally
% in force, and save the text of the mandatory argument
% to its macro for future reference.
%    \begin{macrocode}
  \global\let\dates@@@@read\dates@@@@read@default%
  \global\let\dates@@@read\dates@@@read@default%
  \dates@textcount1%
  \def\theshorttext{#1}%
  \ifnum\dates@textcount=\dates@langnum\relax%
    \gdef\thelongtext{}%
  \fi%
%    \end{macrocode}
% Here is where the funny brace macro referred to above
% comes into play.  We change the catcodes so that
% square-brace-enclosed text will be interpreted as
% a single argument.  Then we look for a brace.  If
% a brace is found, we invoke \cs{dates@@@@@read}
% to read and store the text.  If not, we cut off the
% special category code for square braces and
% call the macro that interprets dates (since we already
% know that we've finished with a date, and have grabbed
% the mandatory text.  Likewise, if we see an \cs{end}
% out there (i.e. there was a curly-brace-enclosed
% mandatory argument right after the date, but it's
% followed immediately by \cs{end}), we also process
% the digested date before proceeding.  Note that the
% \cs{end} in this event will be caught by the lookahead
% machinery at the top of the parsing chain the next time
% around, causing macro recursion to terminate.
%    \begin{macrocode}
  \bgroup%
    \catcode`\[=1\catcode`\]=2\relax%
    \catcode`\<=1\catcode`\>=2\relax%
       \@ifnextnparchar\dates@funny@brace%
         {\dates@@@@@read}%
         {\global\let\thelongtext\theshorttext%
          \@ifnextnparchar\dates@bent@brace%
            {\dates@@@@read@bent}%
            {\egroup%
             \dates@read@exit}%
            {\message{This can't happen}}}%
         {\egroup%
          \dates@read@exit}}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\dates@@@@@read}
% The optional argument uses bog-standard \LaTeX{}
% option syntax.  The only wrinkle is in the
% catcode changes invoked within a group in the
% macro above.  These are cut off by an \cs{egroup} here.
% Apart from that, we just grab the text to a macro,
% and call the macro that does the final processing
% of the date and text information.
%    \begin{macrocode}
\def\dates@@@@@read#1{%
  \egroup%
  \ifnum\dates@textcount=1\relax
    \gdef\thelongtext{#1}%
  \else%
    \ifnum\dates@textcount=\dates@langnum\relax%
      \gdef\thelongtext{#1}%
    \fi%
  \fi%
  \bgroup%
    \catcode`\<=1\catcode`\>=2\relax%
       \@ifnextnparchar\dates@bent@brace%
         {\dates@@@@read@bent}%
         {\egroup%
          \dates@read@exit}%
         {\egroup%
          \dates@read@exit}}
%    \end{macrocode}
% \end{macro}
%    \begin{macrocode}
\def\dates@@@@read@bent#1{%
  \egroup%
  \advance\dates@textcount by1\relax%
  \ifnum\dates@textcount=\dates@langnum\relax
    \def\theshorttext{#1}%
  \fi%
  \bgroup%
    \catcode`\[=1\catcode`\]=2\relax%
    \catcode`\<=1\catcode`\>=2\relax%
       \@ifnextnparchar\dates@funny@brace%
         {\dates@@@@@read}%
         {\ifnum\dates@textcount=\dates@langnum\relax%
            \gdef\thelongtext{}%
          \fi%
          \@ifnextnparchar\dates@bent@brace%
            {\dates@@@@read@bent}%
            {\egroup%
             \dates@read@exit}%
            {\message{This can't happen}}}%
         {\egroup%
          \dates@read@exit}}
%    \end{macrocode}
% \begin{macro}{\dates@read@exit}
% 
%    \begin{macrocode}
\def\dates@read@exit@default{%
  \dates@verify%
  \dates@fix%
  \dates@lastdate\dates@date%
  \ifdates@suppress@global%
  \else%
    \ifdates@suppress%
    \else%
      \dates@action%
    \fi%
  \fi%
  \dates@read}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\dates@verify}
% This macro is used in a few places to verify whether
% all of the necessary date information is present.
% It uses a couple of toggles to allow different bits
% of the address to be confirmed.
%    \begin{macrocode}
\def\dates@verify{%
  \ifnum\dates@month=0%
    \ifdates@requiremonth%
      \PackageError{dates}{Missing month.}{}%
    \else%
      \global\dates@month=1%
    \fi%
  \fi%
  \ifnum\dates@day=0%
    \ifdates@requireday%
      \PackageError{dates}{Missing day of the month.}{}%
    \else%
      \global\dates@day=1%
    \fi%
  \fi%
  \ifnum\dates@year=0\relax%
      \PackageError{dates}{Missing year in ordinary date.}{}%
  \fi}
%    \end{macrocode}
% \end{macro}
%
% \subsection{Selective Handling}
%
% There are three points at which special handling can
% be spliced into the parsing routine.  The defaults of
% these macros have all been presented above.  Below,
% alternative versions internal to the \texttt{dates}
% package itself are set forth.
%
% The following is the default value of "\dates@read@exit".
% It fixes the date, rationalizes the registers
% containing human-readable date information, and
% saves the date for future reference (i.e.~in case
% we need it as the beginning of a range).
% It then performs the action given by the user in the
% argument to "\dateread", and attempts to chain back to continue
% parsing within the presented list of dates.
%
% \subsubsection{Recursive Handling}
%
% \begin{macro}{\dates@read@exit@range}
%
% This is meant to be spliced into the parser immediately
% before the macro:
%
% \begin{quote}
% "\dates@read@exit@default"
% \end{quote}
%
% It is invoked
% by the word "to" in the current date entry.  Invoked
% after the text argument describing the current date
% has been grabbed, it begins by rationalizing the machine
% and human readable dates.  It then expands the registers
% containing the starting and ending long dates describing
% a range into a list macro.  The dates are stepped down one
% and up one day respectively, so that a simple ">" or "<"
% will tell us whether a given date is within a subrange.
% The list macro will later
% be used as a series of bounds
% in the generation of recursive dates and dates
% defined by a function.
%
%    \begin{macrocode}
\def\dates@read@exit@range{%
  \dates@fix%
  \dates@subrange@end\dates@date%
  \dates@reg@a=\expandafter{\dates@subranges}%
  \xdef\dates@subranges{%
    \the\dates@reg@a%
    \noexpand\delim{\the\dates@subrange@start}%
      {\the\dates@date}}%
  \global\let\dates@read@exit\dates@read@exit@default%
  \dates@read@exit}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\dates@read@exit@recurse}
% \begin{macro}{\dates@read@exit@@recurse}
% \begin{macro}{\dates@read@exit@@@recurse}
%
% This is the generic routine for generating dates according
% to a recursively invoked formula.  It is also intended
% for splicing in in front of the macro:
%
% \begin{quote}
% "\dates@read@exit@default"
% \end{quote}
%
%   The first macro in this chain checks
% to be sure that a list of ranges exists.
% It then defines the macro used to delimit the list
% to something that will recurse within a subrange.
% The list macro is then dumped into the document
% for complete expansion.  When it finishes,
% control is passed back to the top, so that
% reading can continue through the list of dates.
%
%    \begin{macrocode}
\def\dates@read@exit@recurse{%
  \expandafter\ifcat\expandafter$\dates@subranges$%
    \PackageError{dates}{No range given}%
      {You need to specify a range before %
       recursive entries and formulae}%
  \fi\relax%
  \ifx\dates@init\relax%
    \ifnum\dates@day>0\relax%
      \dates@everymonth@day\dates@day%
      \ifnum\dates@month>0\relax%
         \dates@everyyear@month\dates@month%
         \global\let\dates@init\dates@init@yearly@doy%
        \global\let\dates@increment\dates@increment@yearly@doy%
      \else%
        \global\let\dates@init\dates@init@monthly@dom%
        \global\let\dates@increment\dates@increment@monthly@dom%
      \fi%
    \else%
      \PackageError{dates}{Incomplete recursive entry}%
       {You need to specify a day of the week or a day of %
        the month or something for entries beginning with %
        the word Every.}
    \fi%
  \fi%
  \global\let\delim\dates@read@exit@@recurse%
  \dates@subranges%
  \dates@read}
%    \end{macrocode}
%
% This is the macro to which "\delim" is set above.
% It sets up registers with the top and bottom boundaries
% of the range, as given in the list, then sets the
% current date to be the bottom of the range.
% It then executes an (arbitrary) function to find
% the first calculated date above the bottom of the range,
% rationalizes the human-readable date registers, and
% performs the user's requested action.  It then chains to
% the macro that will loop until the range is exceeded.
%
%    \begin{macrocode}
\def\dates@read@exit@@recurse#1#2{%
  \dates@subrange@start#1\relax%
  \dates@subrange@end#2\relax%
%  \ifnum\dates@subrange@end>\dates@range@limit%
%    \dates@subrange@end\dates@range@limit%
%  \fi%
  \dates@init%
  \caldate%
  \ifdates@suppress@global%
  \else%
    \ifdates@suppress%
    \else%
        \dates@action%
    \fi%
  \fi%
  \let\next\dates@read@exit@@@recurse%
  \dates@read@exit@@@recurse}
%    \end{macrocode}
%
% This is the macro that does the actual recursion for recursive entries.
% It increments, checks the date, performs the action if appropriate,
% otherwise breaks the loop so that control can pass back to
% "\dates@read@exit@recurse".
%
%    \begin{macrocode}
\def\dates@read@exit@@@recurse{%
  \dates@increment\relax%
  \ifnum\dates@date>\dates@subrange@end\relax%
    \let\next\relax%
  \else%
    \caldate%
    \ifdates@suppress@global%
    \else%
      \ifdates@suppress%
      \else%
        \dates@action%
      \fi%
    \fi%
  \fi%
  \next}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\dates@increment@daily}
%    \begin{macrocode}
\def\dates@increment@daily{%
  \global\advance\dates@date by 1\relax}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\dates@init@weekly}
% \begin{macro}{\dates@increment@weekly}
%
% The following is the initialization macro for weekly recursion.
% It moves to the first instance of the targetted
% day of the week above the bottom of the subrange.
%
%    \begin{macrocode}
\def\dates@init@weekly{%
  \global\dates@date\dates@subrange@start%
  \mod7\dates@date\dates@weekd%
  \dates@three=\dates@weekd@target\relax%
  \advance\dates@three by -\dates@weekd\relax%
  \ifnum\dates@three<0\relax%
    \advance\dates@three by7%
  \fi%
  \global\advance\dates@date by\dates@three\relax}
\def\dates@init@semiweekly{%
  \dates@verify%
  \dates@fix%
  \ifnum\dates@subrange@start>\dates@date%
    \dates@ct@z\dates@subrange@start%
    \advance\dates@ct@z by-\dates@date%
    \mod{14}\dates@ct@z\dates@catch%
    \global\dates@date\dates@subrange@start%
    \global\advance\dates@date by\dates@catch%
  \fi}
%    \end{macrocode}
%
% This is the increment macro used for weekly recursion.
% It just bumps up the date seven days each time it is invoked.
%
%    \begin{macrocode}
\def\dates@increment@weekly{%
  \global\advance\dates@date by7\relax}
\def\dates@increment@semiweekly{%
  \global\advance\dates@date by14\relax}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\dates@init@monthly@dow}
% \begin{macro}{\dates@increment@monthly@dow}
%
% The following is the general initialization macro for finding
% an instance of a day of the week within a month.  It begins
% by setting the value of a macro with which it terminates
% to be "\relax", in the hope that a match will be found
% the first time it is invoked.  We then move the date
% forward, if necessary, to find the targetted day of the week.
% When this is found, we set the human-readable register
% information according to that long date (including the
% day of the month).  Dividing and multiplying by "7" yields
% the largest multiple of "7" that is equal to or less than the
% day of the month.  If this is "0", we're in the first week,
% if "7" we're in the second, and so forth.  If the value
% of the current day is too low, we move up the date.
% If it is too high, we move to the first day
% of the next month, and request a loop back through
% the same routines.
% 
%    \begin{macrocode}
\def\dates@init@monthly@dow{%
  \global\dates@date\dates@subrange@start%
  \dates@init@monthly@@dow}
\def\dates@init@monthly@@dow{%
  \let\dates@init@monthly@dow@recurse\relax%
  \caldate%
  \nextday\dates@weekd@target%
  \caldate%
  \dates@one\dates@day%
  \divide\dates@one by 7\relax%
  \multiply\dates@one by 7\relax%
  \ifnum\dates@modulo>\dates@one\relax%
    \dates@two\dates@modulo%
    \advance\dates@two by -\dates@one%
    \global\advance\dates@date by \dates@two%
  \else%
    \ifnum\dates@modulo<\dates@one\relax%
      \dates@next@month%
      \let\dates@init@monthly@dow@recurse\dates@init@monthly@@dow%
    \fi%
  \fi%
\dates@init@monthly@dow@recurse}
\def\dates@init@monthly@dom{%
  \global\dates@date\dates@subrange@start%
  \dates@init@monthly@@dom}
\def\dates@init@monthly@@dom{%
  \let\dates@init@monthly@dom@recurse\relax%
  \caldate%
  \ifnum\dates@day>\dates@everymonth@day%
    \dates@next@month%
    \let\dates@init@monthly@dom@recurse\dates\init@monthly@@dom%
  \else%
    \global\dates@day\dates@everymonth@day%
    \dates@fix%
  \fi%
  \dates@init@monthly@dom@recurse}
\def\dates@init@yearly@doy{%
  \global\dates@date\dates@subrange@start%
  \dates@init@yearly@@doy}
\def\dates@init@yearly@@doy{%
  \let\dates@init@yearly@doy@recurse\relax%
  \caldate%
  \dates@ct@z\dates@day@offset%
  \global\dates@day\dates@everymonth@day%
  \global\dates@month\dates@everyyear@month%
  \dates@fix%
  \ifnum\dates@ct@z>\dates@day@offset%
    \nextyear%
    \dates@fix%
    \let\dates@init@yearly@doy@recurse\dates@init@yearly@@doy%
  \fi%
  \dates@init@yearly@doy@recurse}
%    \end{macrocode}
%
% This is the general incrementing macro for monthly entries.
% It's pretty simple; we just move to the first day of the
% next month, then run the initialization macro again to
% find the appropriate date within the month.
% 
%    \begin{macrocode}
\def\dates@increment@monthly@dow{%
  \dates@next@month%
  \dates@init@monthly@@dow}
\def\dates@increment@monthly@dom{%
  \dates@next@month%
  \dates@init@monthly@@dom}
\def\dates@increment@yearly@doy{%
  \nextyear%
  \global\dates@month=\dates@everyyear@month\relax%
  \global\dates@day=\dates@everymonth@day\relax%
  \dates@fix%
  \dates@init@yearly@@doy}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\dates@@@read@function}
% \begin{macro}{\dates@@@read@@function}
%
% This is designed to be spliced into the parser
% immediately before the macro:
% 
% \begin{quote}
% "\dates@@@read@default".
% \end{quote}
%
% It is invoked, like the other special handling routines,
% via the "\dates@execute" hook in the text analyzer
% (see \ref{analyze} for details).  It reads two
% arguments immediately following the word that
% triggers it.  It stores these for reference.
% The third argument is read after checking to be
% sure that we have reached the end of the parsing
% string, and are looking at the delimiter that
% ends it.  Then this is gobbled, and dumped into the
% document so that the definitions it contains will
% take effect.  The jiggery-pokery with grouping
% limits the effect of "\makeatletter" to the
% scope of the braces delimiting the user's
% function definition, while the macros he defines
% there can be defined locally.
%
% This third argument should not produce any printed output, and should define,
% at minimum, two macros, the names of which are given as
% the first and second arguments following the invoking
% word in the parsed text.  The first of these will
% initialize to the first date conforming to the formula,
% counting from the bottom of a range of dates, and should
% return a long date in "\dates@date".  The second should
% increment upward one date from a given date, also returning
% the result in "\dates@date".  The demonstration file
% contains a sample of code which calculates the phases of
% the moon.
%
%    \begin{macrocode}
\long\def\dates@@@read@function #1 #2 {%
  \xdef\dates@init{\csname#1\endcsname}%
  \xdef\dates@increment{\csname#2\endcsname}%
  \@ifnextnparchar\dates@serious@brace%
   {\bgroup%
      \makeatletter%
      \expandafter\dates@@@read@@function}%
   {\PackageError%
      {dates}%
      {Extra text after function names}%
      {The third argument must be in curly braces.}}%
   {\relax}}
%    \end{macrocode}
%
%    \begin{macrocode}
\long\def\dates@@@read@@function#1{%
    \long\gdef\dates@temp{#1}%
  \egroup%
  \dates@temp%
  \let\dates@temp\relax%
  \dates@@@@read@default}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \subsection{The Analyzer}
%
% Human-readable dates are fetched word by word by
% the above routines.  The "\dates@@@read@default"
% macro feeds individual words to the analyzer
% described here.
%
% \begin{macro}{dates@analyze}
%
% This
% is a pretty straightforward set of nested
% conditions that will uniquely identify an item
% as a month, a year, a day or a time, and respond
% accordingly.  The macro is somewhat long, so
% comments are provided to indicate nesting
% levels and their functions.
%
%    \begin{macrocode}
\long\def\dates@analyze#1#2#{%
%    \end{macrocode}
%
% \begin{description}
% \item[Level One] Check to see if we're dealing with a number.
% If so, define a macro containing only zero to use in a series of
% parsing checks.
% \end{description}
%
%    \begin{macrocode}
  \ifcat\noexpand#11%
    \def\dates@zero{0}%
%    \end{macrocode}
%
% \begin{description}
% \item[Level Two] Check to see if this is not a range of times.
% \end{description}
%
%    \begin{macrocode}
    \expandafter\dates@check@hyphen\@overword-{}%
    \ifx\dates@arg@b\dates@zero%
%    \end{macrocode}
%
% \begin{description}
% \item[Level Three] It now looks like this either a lone time or
% an integer.  Check to see if it's not a time.  (We use "\@overword",
% but it will have the same content as "\dates@arg@a").
% \end{description}
%
%    \begin{macrocode}
      \expandafter\dates@check@colon\@overword:{}%
      \ifx\dates@arg@b\dates@zero%
%    \end{macrocode}
%
% \begin{description}
% \item[Level Four] Alright, so it's an integer.  That means it's either a year
% or a day of the month.  The instructions require a 4-digit
% year, which is always larger than a day of the month.
% \end{description}
%
%    \begin{macrocode}
          \expandafter\ifnum\@overword>31%
            \setyear{\dates@arg@a}%
          \else%
            \ifnum\dates@day>0%
              \dates@dayerror%
            \else%
              \global\dates@day=\dates@arg@a%
            \fi%
          \fi%
%    \end{macrocode}
%
% \begin{description}
% \item[Level Three (again)] If the item was a lone time, we set variables
% accordingly.
% \end{description}
%
%    \begin{macrocode}
      \else%
        \expandafter\dates@strip@colon\dates@arg@b%
        \global\dates@time@start=\dates@arg@a%
        \global\multiply\dates@time@start by 60%
        \global\advance\dates@time@start by \dates@arg@b%
        \global\dates@time@end=\dates@time@start%
      \fi%
%    \end{macrocode}
%
% \begin{description}
% \item[Level Two (again)] If it was a range of times, we have the
% extremes of the range in "\dates@arg@a" and "\dates@arg@b".
% We process each so that a colon delimiter is not required,
% but will be recognized if given.  Note the "0" in the definition
% of "\dates@check@colon" et al., above; this produces a default of zero
% if this is a bare number with no colon delimiter.
%
% We proceed by first setting aside the contents of "\dates\arg@b"
% so that they will not be overwritten.  We then check for the
% existence of a colon and, if one is found, the trailing
% colon left by the test macro is stripped off.  We then
% set the time.
% \end{description}
%
%    \begin{macrocode}
    \else%
      \expandafter\dates@strip@hyphen\dates@arg@b%
      \let\dates@temp\dates@arg@b%
      \expandafter\dates@check@colon\dates@arg@a:{}%
      \ifx\dates@arg@b\dates@zero%
      \else%
        \expandafter\dates@strip@colon\dates@arg@b%
      \fi%
      \global\dates@time@start=\dates@arg@a\relax%
      \global\multiply\dates@time@start by 60\relax%
      \global\advance\dates@time@start by \dates@arg@b\relax%
%    \end{macrocode}
%
% \begin{description}
% \item[Level Two (continued)] We then do exactly the same thing for the second time
% given.
% \end{description}
%
%    \begin{macrocode}
      \expandafter\dates@check@colon\dates@temp:{}%
      \ifx\dates@arg@b\dates@zero%
      \else%
        \expandafter\dates@strip@colon\dates@arg@b%
      \fi%
      \global\dates@time@end=\dates@arg@a\relax%
      \global\multiply\dates@time@end by 60\relax%
      \global\advance\dates@time@end by \dates@arg@b%
    \fi%
%    \end{macrocode}
%
% \begin{description}
% \item[Level one (again)] If "\dates@word" does not look like a
% number, then it is handled as text.
% We pass control to a macro that will
% simply execute a macro name derived from the first three
% characters of the word.  If it's unknown chaff, it will therefore
% effectively be ignored.  This can be used as a hook
% for defining options not included in the "dates" package
% proper.  The description of the hooks used by the
% vanilla version of "dates" is given below.
% \end{description}
%
%    \begin{macrocode}
  \else%
      \dates@execute#1#2XXX{}%
  \fi}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\dates@execute}
%
% Used as the default action in the analyzer, this just blindly
% executes a macro that may match a day, month or option
% name.  If the date string is limited by "\relax{}",
% the macro name "\relax" will be read in as a token
% for interpretation.  To prevent unexpected results,
% we therefore convert a leading control sequence to a string
% within "\csname" "\endcsname".  We must not give
% the same treatment to non-control-sequence items,
% however, because this would prevent the expansion of
% uppercase characters, which have been read in as active
% characters, to their lowercase counterparts.  An "\ifcat"
% is used to choose which action is appropriate.  The
% macros invoked by "\dates@execute" never take arguments,
% so they can be expanded within the scope of "\ifcat".
%
%    \begin{macrocode}
\def\dates@execute#1#2#3#4#{%
  \ifcat#1\relax%
    \expandafter\csname%
      \string#1#2#3mac\endcsname%
  \else%
    \global\dates@catch=`#1\relax
    \global\advance\dates@catch by-65
    \dates@reg@a=\expandafter{\ifcase\dates@catch
      a\or b\or c\or d\or e\or f\or g\or h\or i\or j\or k\or l\or
      m\or n\or o\or p\or q\or r\or s\or t\or u\or v\or w\or x\or
      y\or z\else #1\fi}
    \csname\the\dates@reg@a#2#3mac\endcsname%
  \fi}%
%    \end{macrocode}
% \end{macro}
%
% \subsection{Fodder for the Analyzer}
%
% As can be gleaned from an examination of "\dates@execute",
% a word is read by executing a macro named using
% its first three letters.  We provide definitions
% for a number of such macros here.
%
% \begin{macro}{\evemac}
%
% "Every" sets up for recursion, and for a default of
% incrementing over days of the week.
%
%    \begin{macrocode}
\def\evemac{%
 \global\let\dates@read@exit=\dates@read@exit@recurse}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\daymac}
%
% The following was suggested by Miroslav Novak, hacked
% together by Frank Bennett in January 1997, but awaited
% final testing while the Timetable package stabilized.
% It was reported to fail by Miroslav on 5 March 1997,
% and a fix was put in place and released by Frank on 6 March.
%
% \begin{macrocode}
\def\daymac{%
  \global\let\dates@init=\dates@init@daily%
  \global\let\dates@increment=\dates@increment@daily}
\def\dates@init@daily{%
  \global\dates@date=\dates@subrange@start}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\othmac}
%
% "Other" will modify the effect of "every" to
% choose every other date within the range, beginning
% with the specified date.  The specified date need not
% be within the range.
%    \begin{macrocode}
\def\othmac{%
  \global\let\dates@init=\dates@init@semiweekly%
  \global\let\dates@increment=\dates@increment@semiweekly}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\firmac}
% \begin{macro}{\secmac}
% \begin{macro}{\thimac}
%
% "First", "second" and "third" will set a counter than controls which
% instance of a day of the week within a month should be chosen,
% and modifies the effect of "every" to recurse on that
% instance within every month, within the subrange.
%    \begin{macrocode}
\def\firmac{%
  \dates@modulo=0%
  \global\let\dates@init=\dates@init@monthly@dow%
  \global\let\dates@increment=\dates@increment@monthly@dow}%
%
\def\secmac{%
  \dates@modulo=7%
  \global\let\dates@init=\dates@init@monthly@dow%
  \global\let\dates@increment=\dates@increment@monthly@dow}%
%
\def\thimac{%
  \dates@modulo=14%
  \global\let\dates@init=\dates@init@monthly@dow%
  \global\let\dates@increment=\dates@increment@monthly@dow}%
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\toXmac}
%
% The following responds to "to" in the parsed text.  If
% the year is zero, it sets
% the bottom of a range to the last date encountered, and
% lets the exit macro for processing a finished date be
% one which will set the top of the range before performing
% the action specified by the user.  
% If the year is greater than zero, we grab the \textit{current}
% date, reset everything to zero, and continue parsing.
% This permits ``no frills'' range designations, as
% in the "calendar" package.
%
% The "X" is appended to
% fill out to three characters.  For reasons that I do not
% fully understand, this was necessary to prevent the
% package from exiting within the scope of a group.
%
%    \begin{macrocode}
\def\toXmac{\relax%
  \ifnum\dates@year=0%
    \dates@subrange@start\dates@lastdate%
  \else%
    \dates@fix%
    \dates@subrange@start\dates@date%
    \global\dates@month=0%
    \global\dates@day=0%
    \setyear{1900}%
  \fi%
  \global\let\dates@read@exit\dates@read@exit@range}%
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\funmac}
%
% The following causes a function definition to be read
% immediately after the word "function" in the date text.
%
%    \begin{macrocode}
\def\funmac{%
  \global\let\dates@read@exit=\dates@read@exit@recurse%
  \global\let\dates@@@read=\dates@@@read@function}
%    \end{macrocode}
% \end{macro}
%
% The following causes the suppression of any action
% in respect of the entry in which it is found.
%
%    \begin{macrocode}
\def\remmac{%
  \global\dates@suppresstrue}
%    \end{macrocode}
%
% \begin{macro}{\janmac}
% \begin{macro}{\jancheckmac}
%
% The months are defined globally using a recursive engine
% that is discarded when the macros have been defined.
% Each month macro first sets a counter to the number of
% days in the month, so that a range check can be performed
% when the date is interpreted.  It then checks to
% see if a month has already been selected, and if so
% it forces a fatal error; otherwise, the month counter
% is set to the appropriate value.
%
%    \begin{macrocode}
\bgroup
  \def\monthdata#1#2#3#4#5\end{%
    \expandafter\gdef\csname#2#3#4mac\endcsname{%
        \ifnum\dates@month>0%
          \dates@montherror%
        \else%
          \global\dates@month=#1%
        \fi}%
    \ifcat$#5$\let\next\@gobble\else\let\next\monthdata\fi%
    \next#5\end}%
%    \end{macrocode}
%
%
% The following does the action generation of month macros.
%    \begin{macrocode}
  \monthdata1jan2feb3mar4apr5may6jun%
            7jul8aug9sep{10}oct{11}nov{12}dec\end
\egroup
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\monmac}
%
% Days of the week are specified in a similar fashion.
%
%    \begin{macrocode}
\bgroup
  \def\weekdata#1#2#3#4#5\end{%
    \expandafter\gdef\csname #2#3#4mac\endcsname{%
      \ifnum\dates@weekd@target<7\relax%
        \dates@weekerror%
      \else%
        \global\dates@weekd@target=#1\relax%
        \ifx\dates@init\relax%
          \global\let\dates@init\dates@init@weekly%
        \fi%
        \ifx\dates@increment\relax%
          \global\let\dates@increment\dates@increment@weekly%
        \fi%
      \fi}%
    \ifcat$#5$\let\next\@gobble\else\let\next\weekdata\fi%
    \next#5\end}
  \weekdata0sun1mon2tue3wed4thu5fri6sat\end
\egroup
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\dates@montherror}
% \begin{macro}{\dates@weekerror}
% \begin{macro}{\dates@dayerror}
%
% These three macros are used in the above definitions
% to produce error messages if something is wrong
% with a date.
%
%    \begin{macrocode}
\def\dates@montherror{%
  \PackageError{dates}{Month multiply defined}{%
    You have set the month more than once here.}}
\def\dates@dayerror{%
  \PackageError{dates}{Day multiply defined}{%
    You have set the day more than once here.}}
\def\dates@weekerror{%
  \PackageError{dates}{Week multiply defined}{%
    You have set the day of the week more than once here.}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{Low-level Bits and Pieces}
%
% \begin{macro}{\dates@capsdown}
%
% The "\lowercase" function provided in \TeX{} does not
% operate in \TeX{}'s mouth, and so cannot be used to
% create lowercase strings for export to a non-DVI
% file or for display on the terminal.
% We can get around this problem by 
% making all upper-case characters
% active, and defining them to lowercase themselves.  The
% operative definition is "\dates@capsdown".
% The
% grouping culls the bootstrapping definitions used to
% create these macros from memory.  A detailed explanation
% these macros is not given here, but they do work.
% Essentially, they function by looping over sets of three
% characters, two uppercase and one lowercase, building a
% macro ("\dates@capsdown") that will make the uppercase
% characters in the list locally active, with the appropriate
% definition.  Two uppercase characters are required in the
% list because on is read to identify the character so
% that it can be made active in order, on the second read,
% to take its active form and define it.
%
%    \begin{macrocode}
%<*cull>
\bgroup
\dates@reg@a={}
\gdef\dates@capsdown{}
\def\dates@capsactive#1{%
  \ifx#1\end%
    \let\next\relax%
  \else%
    \catcode`#1=13%
    \let\next\dates@@capsactive%
  \fi%
  \next}
\def\dates@@capsactive#1#2{%
  \dates@reg=\expandafter{%
    \dates@capsdown\catcode`#1=13\def#1{#2}}%
  \xdef\dates@capsdown{\the\dates@reg}%
  \let\next\dates@capsactive%
  \next}
\dates@capsactive%
  AAaBBbCCcDDdEEeFFfGGgHHhIIiJJjKKk%
  LLlMMmNNnOOoPPpQQqRRrSSsTTtUUuVVv%
  WWwXXxYYyZZz\end
\egroup
%</cull>
%    \end{macrocode}
% \end{macro}
%
% For parsing strings, we use some little
% macros to identify strings that have a colon in
% them (which will be assumed to be a time)
% or a hyphen (assumed to be a range of times),
% and to strip those off where necessary.
%
%    \begin{macrocode}
\def\dates@check@colon#1:#2#{%
  \def\dates@arg@a{#1}%
  \def\dates@arg@b{0#2}}
\def\dates@strip@colon#1:{%
  \def\dates@arg@b{#1}}
\def\dates@check@hyphen#1-#2#{%
  \def\dates@arg@a{#1}%
  \def\dates@arg@b{0#2}}
\def\dates@strip@hyphen#1-{%
  \def\dates@arg@b{#1}}
%    \end{macrocode}
%
% The following macro is used to terminate
% processing.
%
%    \begin{macrocode}
\expandafter\expandafter\expandafter\def%
  \expandafter\csname%
    \string\relaxXXmac\endcsname{%
      \global\let\dates@@@@read\relax}
%    \end{macrocode}
%
%
%
% \subsection{Interface Macros for Date Info}
%
% \begin{macro}{\theyear}
% \begin{macro}{\themonth}
% \begin{macro}{\theshortmonth}
% \begin{macro}{\themonthnumber}
% \begin{macro}{\theday}
% \begin{macro}{\theweekday}
% \begin{macro}{\theshortweekday}
% \begin{macro}{\thelongdate}
% \begin{macro}{\themonthdays}
% \begin{macro}{\theshorttext}
% \begin{macro}{\thelongtext}
%
% \label{interface} These macros can be used to include date information
% in the text fed to "\dateread".  They do not contain
% unprintable operations, and so can be used to display
% text on the terminal as well as in a document.  All
% are updated from the long date by the "\caldate" command.
% The macros "\theshorttext" and "\thelongtext" are
% defined elsewhere on the fly; token registers cannot
% be used for these because they must be allowed to
% expand fully on the terminal.
%
%    \begin{macrocode}
\def\theyear{\the\dates@year@full}
% \def\themonth{\the\dates@monthname}
% \def\theshortmonth{\the\dates@monthname}
\def\themonthnumber{\the\dates@month}
\def\theday{\the\dates@day}
% \def\theweekday{\the\dates@dayname}
% \def\theshortweekday{\the\dates@shortweekday}
\def\thelongdate{\the\dates@date}
\def\themonthdays{\the\dates@days}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{Maths Functions for Dates}
%
% The following code is an almost direct rip-off of the
% "calendar" macros for plain \TeX{} that are stored on
% CTAN.  If anyone knows who the author is, I will be happy
% to include a credit here.  I have made scant effort
% to document the code, but it works well.
%
% \begin{macro}{\setyear}
%
% Set the current year.
%
%    \begin{macrocode}
\def\setyear#1{\dates@year=#1%
 \advance\dates@year by -1900\calculateyearbase}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\nextyear}
%
% Advance by one year
%
%    \begin{macrocode}
\def\nextyear{\advance\dates@year by1%
 \calculateyearbase}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\dates@next@month}
% Advance by one month.
%
%    \begin{macrocode}
\def\dates@next@month{%
  \ifnum\dates@month=12%
    \advance\dates@year by 1\calculateyearbase%
    \global\dates@month=1%
    \global\dates@day=1%
  \else%
    \global\advance\dates@month by 1%
    \global\dates@day=1%
  \fi%
  \dates@fix}
%    \end{macrocode}
% \end{macro}
% 
% Set the current time zone.
%
% \begin{macro}{\settimezone}
%    \begin{macrocode}
\def\settimezone#1{\dates@timezone=#1%
 \multiply\dates@timezone by 1000%
 \divide\dates@timezone by24}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\calculateyearbase}
%
% Set the "\ifleapyear" toggle.  Set "\dates@yearbase" to the number of
% days passed from 1900, Jan 0 to New year's date in the target year.
%
%    \begin{macrocode}
\def\calculateyearbase{%
 \global\dates@yearbase=-1%
 {\dates@ct@z=\dates@year\divide\dates@ct@z by4%
 \multiply\dates@ct@z by4\relax%
 \ifnum\dates@year=\dates@ct@z%
   \global\dates@catch=0%
 \else%
   \global\dates@catch=1%
 \fi}%
 \ifcase\dates@catch \leapyeartrue\or%
  \leapyearfalse\fi%
 {\dates@ct@z=\dates@year\multiply\dates@ct@z%
 by1461\advance\dates@ct@z by3%
 \divide\dates@ct@z by4%
 \global\dates@catch=\dates@ct@z}%
 \global\advance\dates@yearbase by\dates@catch\relax%
 \ifnum\dates@year=0\global\dates@yearbase=0\leapyearfalse\fi}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\monthdays}
%
%  Set the number of days passed at the end of each month in "\dates@day".
%
%    \begin{macrocode}
\def\monthdays{%
\global\dates@catch\ifcase\dates@month%
  0\or31\or%
  59\or90\or120\or151\or181\or212\or%
  243\or273\or304\or334\or365\fi%
 {\ifleapyear\ifnum\dates@month>1%
  \global\advance\dates@catch by1\fi\fi}%
%  ??????????? ************ global okay here?
 \global\dates@day@offset=\dates@catch}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\dates@fix}
%
% Return the long date of "\dates@month", "\dates@day" in the year "\dates@year"
% in "\dates@date" after checking to be sure that the month and the day
% have been set, if confirmation has been toggled on, and that
% the number of days
% in the month conforms to the constraints of reality.
%
% This can now be invoked by itself; there is no need to follow
% it with \cs{caldate}.
%    \begin{macrocode}
\def\dates@fix{%
 \dates@year@get%
 \dates@monthname@get%
 \ifnum\dates@days<\dates@day%
   \PackageError{dates}{Day of month out of range}{%
     There are only \the\dates@days\space days in %
     \themonth, but you have tried^^J%
     to specify \the\dates@day.}%
 \else%
   \global\dates@date=\dates@day{\advance\dates@month by-1%
    \monthdays%
    \global\advance\dates@date by\dates@day@offset%
    \global\advance\dates@date by\dates@yearbase}%
 \fi%
 \dates@dayname@get}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\mod}
%
% Long date "MOD 7" will give the week day.
% Sunday is "0" and Saturday is "6".  The base
% number is returned in "\dates@three",
% the mod in "#3".
%
%    \begin{macrocode}
\def\mod#1#2#3{\dates@three=#2\relax%
 \dates@four=\dates@three%
 \divide\dates@three by#1%
 \multiply\dates@three by#1%
\advance\dates@four by-\dates@three%
 #3=\dates@four}

\def\dates@year@get{%
  \global\dates@year@full\dates@year%
  \global\advance\dates@year@full by 1900\relax}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\theweekday}
%
% Set the names of week day (Local).
%
%    \begin{macrocode}
\def\dates@dayname@get{\mod7\dates@date\dates@weekd}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\caldate}
%
% Gives the usual calendar date for
% a long date in counter "\dates@date".
% Returned in "\dates@day", "\dates@month" and "\dates@year"
% and other registers.  See the interface macros above
% under \ref{interface}.
%
%    \begin{macrocode}
\def\caldate{\dates@year=\dates@date%
 \multiply\dates@year by4\divide\dates@year by1461%
 \calculateyearbase%
 {\advance\dates@date by-\dates@yearbase\global\dates@month=0%
 \loop\monthdays\ifnum\dates@day@offset<\dates@date%
 \global\advance\dates@month by1\repeat%
 {\advance\dates@month by-1\monthdays%
 \advance\dates@date by-\dates@day@offset%
 \global\dates@day=\dates@date}}%
 \dates@year@get%
 \dates@monthname@get%
 \dates@dayname@get}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\dates@monthname@get}
%
% This stores the names of the months to registers.
% It is run by "\caldate".  The definition here
% is performed in the alternative, depending upon
% the value of the "\dates@language" counter.  This
% counter is set in the options section.  Packages 
% which draw on the Dates package (such as Calendar,
% and the various Calendar style packages) can pass
% the language options down to the Dates package through
% the standard \LaTeXe{} package interface.  Because Japanese
% high-bit code may case a non-Japanese version of
% \LaTeXe to fail, we allow for its exclusion here.
% The odd structure of this is necessary to cope with the
% fact that the "\ifcase" function is blind to the nesting
% of case conditions.
%    \begin{macrocode}
% Japanese removed.
\def\dates@monthname@get{%
  \ifcase\dates@month%
    \or%
        \global\dates@days=31\relax%
    \or%
        \ifleapyear%
          \global\dates@days=29\relax%
        \else%
          \global\dates@days=28\relax%
        \fi%
    \or%
        \global\dates@days=31\relax%
    \or%
        \global\dates@days=30\relax%
    \or%
        \global\dates@days=31\relax%
    \or%
        \global\dates@days=30\relax%
    \or%
        \global\dates@days=31\relax%
    \or%
        \global\dates@days=31\relax%
    \or%
        \global\dates@days=30\relax%
    \or%
        \global\dates@days=31\relax%
    \or%
        \global\dates@days=30\relax%
    \or%
        \global\dates@days=31\relax%
  \fi}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\nextday}
%
% Find the next (previous) day after
% (before) "\dates@date" with "\mod7=#1".
%
%    \begin{macrocode}
\def\nextday#1{{\dates@ct@z=#1\mod7\dates@date\dates@weekd%
 \advance\dates@ct@z by-\dates@weekd\relax%
 \ifnum\dates@ct@z<0\advance\dates@ct@z by7\fi%
 \global\advance\dates@date by\dates@ct@z}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\prevday}
%
%    \begin{macrocode}
\def\prevday#1{\snextday#1%
 \global\advance\dates@date by-7}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\snextday}
%
%    \begin{macrocode}
\def\snextday#1{\global\advance\dates@date by1%
 \nextday#1}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\sprevday}
%
%    \begin{macrocode}
\def\sprevday#1{\global\advance\dates@date by-1%
 \prevday#1}
%    \end{macrocode}
% \end{macro}
%
% Convert from Julian date and time in
% \date to long date (in local time) 
%
%    \begin{macrocode}
\def\jdttol{\advance\dates@date by500%
%\message{Ran jdttol^^J}%
 \advance\dates@date by\dates@timezone%
 \global\divide\dates@date by1000}
%    \end{macrocode}
%
% \subsection{Trigonometric Functions}
%
%    \begin{macrocode}
\def\sintable#1{\ifcase #1 0\or100\or199%
 \or296\or389\or479\or565\or644\or717%
 \or783\or841\or891\or932\or964\or985%
 \or997\or1000\or992\or974\or946\or909%
 \or863\or808\or746\or675\or598\or516%
 \or427\or335\or239\or141\or42\or-58%
 \or-158\fi}
%    \end{macrocode}
%
% Reduces modulo "2\pi" (requires positive
% argument theta):
% "theta := theta" "MOD 2\pi", where
% "theta = count1*10^(-3)"
%
%    \begin{macrocode}
\def\twopimod{\count2 =\count1%
 \divide\count2 by6284 \count3 =1853%
 \count4 =6283\multiply\count3  by\count2%
 \multiply\count4  by\count2%
 \divide\count3  by10000%
 \advance\count3  by\count4%
 \advance\count1  by-\count3}%
%    \end{macrocode}
%
% "v := sin(theta)", where
% "v = count4*10^(-3)";
% "theta = count1*10^(-3)"
% theta is reduced "MOD 2\pi" to be
% "0<=theta<2\pi" by "\TWOPIMOD",
% then linear interpolation is performed
% using "\SINTABLE".
%
%    \begin{macrocode}
\def\sin{\relax%
 \ifnum\count1<0 \signtrue%
 \count1=-\count1\else \signfalse\fi%
 \loop\ifnum\count1>6284\twopimod\repeat\relax%
 \ifnum\count1>3142%
 \advance\count1 by-3142%
 \ifsign\signfalse\else\signtrue\fi\fi%
 \multiply\count1  by10\count3=\count1%
 \divide\count3  by1000\count2=\count3%
 \multiply\count3  by1000%
 \advance\count3  by-\count1  %
 \count5 =\sintable{\count2 }%
 \count4 =\count5\advance\count2  by1%
 \advance\count4  by -\sintable{\count2}%
 \multiply\count4  by\count3%
 \divide\count4  by1000%
 \advance\count4  by\count5%
 \ifsign\count4 =-\count4\fi}%
%    \end{macrocode}
%
% "v := cos(theta)", where
% "v = count4*10^(-3)";
% "theta = count1*10^(-3)".
% "\SIN" is evaluated on "pi/2-theta".
%    \begin{macrocode}
\def\cos{\advance\count1  by-1571%
 \multiply\count1  by-1\sin}%
%    \end{macrocode}
% Linear transformation of T giving
% "theta := a*T+b", where
% "T = dates@ct@z*10^(-6)";
% "theta = count1*10^(-3)";
% "a = #1*10^3+#2+#3*10^(-3)";
% "b = #4*10^(-3)"
%
%    \begin{macrocode}
\def\lin#1.#2.#3+#4.{\count1=#3%
 \count2=#2\count3=#1%
 \multiply\count1 by\dates@ct@z%
 \multiply\count2 by\dates@ct@z\relax%
 \multiply\count3 by\dates@ct@z%
 \divide\count1 by1000%
 \advance\count1 by\count2%
 \divide\count1 by1000%
 \advance\count1 by\count3%
 \advance\count1 by #4\relax}
%    \end{macrocode}
%
% Accumulate value returned by a
% trigonometric function, scaled by
% factor f, into count6:
% "ac := ac+f*v", where
% "ac = count6*10^(-7)"
% "v = value" of "SIN" or "COS =count4*10^(-3)"
% "f = #1*10^(-4)"
%
%    \begin{macrocode}
\def\fac#1{\multiply\count4  by #1%
 \advance\count6  by\count4}
\def\id{\count4=\count1}  % Identity
%    \end{macrocode}
%
% \subsection{Initialization}
%
% Before anything further is executed, the following registers
% and macros need to be in place.
%
%    \begin{macrocode}
\newcount\dates@textcount
\newcount\dates@ct@z
\newcount\dates@range@limit
\newcount\dates@year
\newcount\dates@timezone
\dates@timezone=0
\newcount\dates@catch
\newcount\dates@day
\newcount\dates@day@offset
\newcount\dates@everymonth@day
\newcount\dates@everyyear@month
\newcount\dates@month
\newcount\dates@date
\newcount\dates@date@current
\newcount\dates@three
\newcount\dates@four
\newcount\dates@weekd
\newcount\dates@time@start
\newcount\dates@time@end
\newcount\dates@subrange@start
\newcount\dates@subrange@end
\newcount\dates@days
\newcount\dates@lastdate
\newcount\dates@yearbase
\newcount\dates@weekd@target
\newcount\dates@modulo
\newcount\dates@year@full
\newcount\dates@extra@day
\newtoks\dates@reg
\newtoks\dates@dayname
\newtoks\dates@shortweekday
\newtoks\dates@monthname
\newtoks\dates@shortmonthname
\newif\ifdates@requiremonth
\newif\ifdates@requireday
\newif\ifdates@suppress
\newif\ifdates@suppress@global
\newif\ifleapyear
\let\delim\relax
\let\dates@serious@brace={
\def\dates@empty{}
%</style>
%    \end{macrocode}
%
%\iffalse
%
% \section{Demonstration File}
%
%    \begin{macrocode}
%<*demo>
\documentclass{minimal}
\usepackage{dates}
\begin{document}

\makeatletter
%
% We say HI to the user
\message{^^J---------------------------------------------------------}
\message{This is a demonstration file for the LaTeX dates package.}
\message{It will print a number of dates to the terminal.^^J}
\message{The code demonstrated by this package is not intended}
\message{for direct use by humans, so I have not worked very hard}
\message{to make its output look pretty, and it won't actually}
\message{print anything.  But if you get a cluttered list of dates}
\message{and no error messages, the package is working for you.}
\message{---------------------------------------------------------}
%
% We invoke the \dateread command.
%
\dateread
%
% We tell it to report a few details to the terminal.
%
{\message{\theshorttext}%
 \message{\theday/\the\dates@month/\the\dates@year}%
 \ifx\thelongtext\dates@empty%
 \else%
   \message{\thelongtext}%
 \fi}
%
% The following are ranges.
%
   december 10 1995 {Start of First Period of Time}
to jan     10 1996 {End of First Period of Time}
   december 10 1996 {Start of Second Period of Time}
to jan     10 1997 {End of Second Period of Time}
%
% The following are specific dates (obviously)
%
February 18 1997 {Frank's Next Birthday}
 [The best presents come in small packages.^^JIt
  would be a terrific present for someone to make
  this one smaller.]
February 18 1998 {Frank's Next Birthday But One}
%
% These are a couple of recursive dates.
%
Every Monday {(Monday Coffee)}
Every Third Tuesday {(Third Tuesday Meeting)}
Function moonsinit moonsincrement {%
  \global\dates@date=\dates@subrange@start%
  \caldate%
  \newcount\moonno%
 \newif\ifsign%
  \def\firstmoon{\moonno=\dates@year
  \multiply\moonno by123685
  \divide\moonno by10000
  \multiply\moonno by4\advance\moonno by-1
  \loop\moondate\relax
  \ifnum\dates@date<\dates@subrange@start
  \advance\moonno by1\repeat}
% Compute date for cycle quarter MOONNO
  \def\moondate{{\dates@ct@z=\moonno
  \lin 202.126.369+0.\dates@ct@z=\count1
  \count6=0
  \lin 0.2.319+2907.\sin\fac{3}
  \divide\count6  by1000
  \lin 365.249.86+7593.\id\fac{1}
  \divide\count6 by10\count7 =\count6
  \ifodd\moonno\quarters
  \else\fullornew\fi\global\dates@date=\count7}
  \jdttol}
% Correction for full and new moon
  \def\fullornew{\count6=0
  \lin -393.0.0+0.
  \divide\count1 by100000000
  \advance\count6  by\count1
  \lin 0.628.300+6269.\sin
  \multiply\count6  by\count4
  \lin -7.-700.-369+  928.\sin\fac{  -74}
  \lin  0. 628. 300+ 6269.\sin\fac{ 1734}
  \lin  1. 256. 600+12539.\sin\fac{   21}
  \lin  8. 328. 670+ 5341.\sin\fac{-4068}
  \lin  8. 538. 220+-4597.\sin\fac{   10}
  \lin  8. 956. 970+11610.\sin\fac{  -51}
  \lin 16. 238. 589+-5526.\sin\fac{   -4}
  \lin 16. 657. 340+10682.\sin\fac{  161}
  \lin 16. 866. 890+  743.\sin\fac{  104}
  \lin 17. 285. 640+16951.\sin\fac{   50}
  \lin 17. 495. 190+ 7013.\sin\fac{    4}
  \lin 24. 986.  10+16023.\sin\fac{   -4}
  \lin 25. 195. 560+ 6084.\sin\fac{   -6}
  \divide\count6  by10000
  \advance\count7 by\count6 }
% Correction for quarters
  \def\quarters{\lin -393.0.0+0.
  \divide\count1  by100000000
  \count6 =\count1  \lin 0.628.300+6269.
  \sin\multiply\count6  by\count4
  \lin -16. -29. -40+-4413.\sin\fac{   40}
  \lin  -7.-700.-369+  928.\sin\fac{  -47}
  \lin  -7. -72. -69+ 7198.\sin\fac{  -30}
  \lin   0. 628. 300+ 6270.\sin\fac{ 1721}
  \lin   1. 256. 600+12539.\sin\fac{   21}
  \lin   8. 328. 670+ 5341.\sin\fac{-6280}
  \lin   8. 538. 220+-4598.\sin\fac{   21}
  \lin   8. 956. 970+11611.\sin\fac{ -119}
  \lin  16. 238. 589+-5526.\sin\fac{   -4}
  \lin  16. 657. 340+10682.\sin\fac{   89}
  \lin  16. 866. 890+  743.\sin\fac{   79}
  \lin  17. 285. 640+16952.\sin\fac{    3}
  \lin  17. 495. 190+ 7013.\sin\fac{    3}
  \lin  24. 986.  10+16023.\sin\fac{   -4}
  \lin  25. 195. 560+ 6085.\sin\fac{   -6}
  \count8=\count6\count6=28000
  \lin 628. 300. 373+ 6270.\cos\fac{   -4}
  \lin   8. 328. 670+ 5341.\cos\fac{    3}
  \count2=\moonno
  \advance\count2 by-1\divide\count2 by2
  \ifodd\count2\multiply\count6  by-1 \fi
  \advance\count6 by\count8
  \divide\count6  by10000
  \advance\count7  by\count6 }
% Events for phases.
% Uses PHASE (local).
  \def\phase{{\dates@ct@z=\moonno
  \count1=\moonno
  \divide\dates@ct@z by4\multiply\dates@ct@z by4
  \advance\count1 by-\dates@ct@z\relax
  \xdef\themoon{\ifcase\count1
  New Moon\or First Quarter\or
  Full Moon\or Last Quarter\fi}}}
  \gdef\moonsinit{%
  \firstmoon
  \global\dates@month=12\global\dates@day=31\dates@fix\global\advance\dates@date by1
  \count1=\dates@date
  \moondate
  \phase
  \caldate}
  \gdef\moonsincrement{%
  \advance\moonno by 1
  \moondate\phase
  \caldate}
  }
  {\themoon}
\end{document}
%</demo>
%    \end{macrocode}
% \section{The Installation File}
%    \begin{macrocode}
%<*installer>
\def\batchfile{dates.ins}
\input docstrip.tex

\keepsilent

\preamble

This file is part of the Dates package.
Copyright (C) 1996, 1997 Frank Bennett, Jr.
All rights reserved.
------------------------------------------
This is a generated file.

IMPORTANT NOTICE:

You are not allowed to change this file.  You may however copy
this file to a file with a different name and then change the
copy if (a) you do not charge for the modified code, (b) you
acknowledge the author(s) in the new file, if it
is distributed to others, and (c) you attach these same
conditions to the new file.

You are not allowed to distribute this file alone.  You are not
allowed to take money for the distribution or use of this file
(or a changed version) except for a nominal charge for copying
etc.

You are allowed to distribute this file under the condition that
it is distributed with all of its contents, intact.

For error reports, or offers to help make this a more powerful,
friendlier, and better package, please contact me on
`fb' at soas.ac.uk

\endpreamble

\generate{\file{dates.sty}   {\from{dates.dtx}{style}}
   }

\generate{\file{demodate.tex}   {\from{dates.dtx}{demo}}
   }

\Msg{***********************************************************}
\Msg{*}
\Msg{* To finish the installation, you have to move the following}
\Msg{* file into a directory searched by TeX:}
\Msg{*}
\Msg{* \space\space dates.sty}
\Msg{*}
\Msg{***********************************************************}

%</installer>
%    \end{macrocode}
%\fi
% \Finale \PrintChanges