path: root/macros/latex/contrib/dates/dates.dtx

%\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
% 
%<*dtx>
          \ProvidesFile{dates.dtx}
%</dtx>
%<style>\NeedsTeXFormat{LaTeX2e}[1995/06/01]
%<style>\ProvidesPackage{dates}
%<style>          [1997/02/17 v1.3 Dates parsing support (Frank Bennett)]
% \fi
%
% \def\fileversion{v1.3}
% \def\filedate{1997/02/17}
%
%
% \iffalse
%<*driver>
\documentclass{ltxdoc}
%\CodelineIndex
%
%\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}{1996/12/27}{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.}
%
% \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
%
% \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}
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% \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}
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% \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}
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% \DoNotIndex{\clearpage,\closein,\lowercase,\@inlabelfalse}
% \DoNotIndex{\selectfont,\mathcode,\newmathalphabet,\rmdefault}
% \DoNotIndex{\bfdefault}
% \setcounter{StandardModuleDepth}{1}
% \DeleteShortVerb{\|}
% \MakeShortVerb{\"}
%
% \begin{abstract}
% \noindent This package provides two low-level macros for the parsing of text
%  using \LaTeXe{}.
% \end{abstract}
%
%
% \CheckSum{1737}
%
% \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).
% If other applications are found for this package,
% that is all to the good.  Put my name on it,
% let me know, and we'll have a drink together sometime.
%
% This user guide is brief, because the parser is
% flexible enough that a long catalogue of strictures
% is unnecessary.  The next section describes the syntax
% for entering dates.  It is followed by a brief description
% of how the macro can be called upon in another package,
% and notes on extending the parser to provide enhanced
% functionality.  I have also provided guidance notes
% in the code itself.
%
% \InputIfFileExists{datesynt}
%  {}
%  {\PackageError{calendar}
%    {Unpack dates.dtx before printing these docs.}
%    {}}
%
%
% \section{Calling the Parser}
%
% As mentioned above, the short description in curly
% braces can only contain plain text.  Printing of
% variable text (such as the text of the date) is
% done through 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.  Go to the code and commentary
% section for further details.
%
% 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 then confirm the existence
% of the file, then run "\inputandread".
%
% \section{Extending the Parser}
%
% 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.
%
%\StopEventually{\PrintIndex}
%
% \section{The Macros}
%
% \subsection{External Utilities}
%
% \begin{macro}{\@ifoverword}
%
% A macro for breaking strings into words is provided by
% a package distributed separately.
%
%    \begin{macrocode}
%<*style>
\RequirePackage{overword}
%    \end{macrocode}
% \end{macro}
%
% \subsection{The Engine Core}
%
% \begin{macro}{\dateread}
% \begin{macro}{\date@read}
% \begin{macro}{\date@@read}
% \begin{macro}{\date@@@read}
% \begin{macro}{\@gobble@enditalls}
%
% The interface macro starts by setting "\dates@action"
% to be its first argument.  It then opens with the initialization
% of variables that are zeroed only at the start of a run
% of dates, and passes control to the next macro in the chain.
% At this point dates are unsorted, so an alternative
% format such as HTML should \textit{not} be generated
% by the argument text, unless you have a filter for sorting
% the text after \TeX{} exits.  In normal use,
% events should be sorted and selected
% first, in the package that calls
% "dates.sty".  The argument can be used to choose
% between modes of \LaTeX{} handling, however.  For example,
% you might want to export the text to a file, or
% store it directly into a list macro.  By inserting a "\let"
% into the hook in "\dates@analyze", you can put toggles
% into the event files themselves.  This is used in "calendar"
% to provide for the selective ``freezing'' of events files
% in a pre-processed form.
%
%    \begin{macrocode}
\long\gdef\dateread#1{%
  \csname dates@reset@longtext\endcsname%
  \let\dates@read\dates@read@default%
  \gdef\dates@action{#1}%
  \def\dates@subranges{}%
  \dates@subrange@start=0%
  \dates@subrange@end=0%
  \dates@read}
%    \end{macrocode}
%
% The next macro continues with initialization, and
% makes uppercase characters active inside a group. 
% Square braces are made grouping characters, so that
% when the next chained macro runs
% and grabs everything up to the next curly brace,
% we will have a means of grouping within the
% grabbed text.  Square braces will be used for
% grouping in user-defined functions for the automatic
% generation of dates.
%
%    \begin{macrocode}
\long\gdef\dates@read@default{%
  \dates@time@start=0%
  \dates@time@end=0%
  \setyear{1900}%
  \dates@month=0%
  \dates@day=0%
  \dates@weekd@target=7%
  \def\theshorttext{}%
  \def\thelongtext{}%
  \dates@suppressfalse%
  \global\let\dates@init\relax%
  \global\let\dates@increment\relax%
  \let\dates@@@read=\dates@@@read@default%
  \let\dates@@@@read=\dates@@@@read@default%
  \let\dates@read@exit=\dates@read@exit@default%
  \bgroup%
    \dates@capsdown%
    \dates@@read}
%    \end{macrocode}
%
% Once we have the text with the catcodes set appropriately,
% we cut off the catcode change and run a macro in front of
% the gobbled text which will chew it up while looping.
% The "\enditall" terminator is a misnomer, really; it
% ends the parsing of a single date, but we will continue
% parsing until "\end" or "\relax{}" are encountered.
%
%    \begin{macrocode}
\long\def\dates@@read#1#{%
    \let\end\relax%
    \xdef\cal@temp{#1 }%
  \egroup%
  \expandafter\dates@@@read\cal@temp\enditall}
%    \end{macrocode}
%
% The following macro does the chewing.  The macro
% "\dates@analyze" will alter the values of
% "\dates@@@read" and of "\dates@read@exit"
% to achieve special effects.  Any hooks that
% redefine these functions should chain to
% their defaults, which end in "@default".
%
%    \begin{macrocode}
\def\dates@@@read@default{%
    \@ifoverword\enditall%
      {\expandafter\dates@analyze\@overword{}%
       \@gobble@enditalls}%
      {\expandafter\dates@analyze\@overword{}%
       \dates@@@read}%
      {\expandafter\dates@analyze\@overword{}%
       \ifnum\dates@year>0%  If date exists, process
         \let\dates@read\relax%       ... and expire
         \dates@read@exit%   May be a range, so not default
       \fi%
       \expandafter\end\@gobbletwo}}%
%    \end{macrocode}
%
% Package extensions that import files on the fly may
% produce multiple "\enditall"s in the scan text for
% a date.  This will chomp all of them.  The change involves
% introducing the following macro via the second
% argument to "\@ifoverword", above.
% \changes{v1.1}{1996/12/21}{Added handler for multiple enditall's.}
%
%    \begin{macrocode}
\def\@gobble@enditalls#1{%
  \@ifnextnparchar\enditall%
   {\let\next\@gobble@enditalls%
    \next}%
   {\dates@@@@read}%
   {\message{This can't happen}}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{Selective Handling}
%
% \subsubsection{Defaults}
%
% There are three points at which special handling can
% be spliced into the parsing routine.  Below, the defaults
% are presented first, followed by alternatives that are
% built into the package.  Other special handling routines
% can be spliced in, as discussed below under \ref{analyze}.
%
% \begin{macro}{\dates@@@@read}
% \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".
%
% There are some dirty tricks here involving the square
% brace.  We define the macro globally inside a group,
% so that our catcode change will not affect other
% code.  Then we set the open brace to be a grouping
% character like "{".  We can't use this inside the
% definition directly (because \TeX{} will try to keep reading
% text until it finds the matching brace), so we "\let"
% a macro have this token's value.  The "\let" is
% global because the value of "{" is global.
% Then we use the funny brace macro inside the
% definition to look for a square brace coming up.
%
% All of this jiggery-pokery is necessary because
% the "\futurelet" command (used by "\@ifnextchar") will stamp
% a category code on the brace when it sees it.
% The end result, though, is that \TeX{} will
% read all the way to the last closing square
% brace, not just to the next one it finds.
% Any square braces inside the text will disappear
% in printed text, but at least the user will not
% find the style blowing up in his face.
%
% We also make capital letters active, with "\dates@capsdown".
% This is done in a separately nested group, so that
% it can be turned off before reading any square-braced
% text, without affecting the catcode of the braces.
%
%    \begin{macrocode}
\bgroup
  \catcode`\[=1
  \global\let\dates@funny@brace=[
  \gdef\dates@@@@read@default#1{%
   \def\theshorttext{#1}%
   \bgroup%
     \catcode`\[=1\catcode`\]=2\relax%
     \bgroup%
       \dates@capsdown%
       \@ifnextnparchar\dates@funny@brace%
         {\egroup%
          \dates@@@@@read}%
         {\egroup%
          \egroup%
          \dates@read@exit}%
         {\egroup%
          \egroup%
          \dates@read@exit}}
\egroup
%    \end{macrocode}
%
% 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 here.
%
%    \begin{macrocode}
\def\dates@@@@@read#1{%
  \egroup%
  \iflongtext%
    \def\thelongtext{#1}%
  \fi%
  \dates@read@exit}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% The following is the default value of "\dates@read@exit".
% It fixes the date and rationalizes the registers
% containing human-readable date information, and
% saves the date for future reference (i.e.~in case
% we need it as the bottom end of a range).
% It then performs the action given by the user in the
% argument to "\dates@read", and chains back to continue
% parsing within the presented list of dates.
%
%    \begin{macrocode}
\def\dates@read@exit@default{%
  \dates@fix%
  \caldate%
  \dates@lastdate\dates@date%
  \ifdates@suppress@global%
  \else%
    \ifdates@suppress%
    \else%
%      \bgroup%
%      \dates@capsup%
        \dates@action%
%      \egroup%
    \fi%
  \fi%
  \dates@read}
%    \end{macrocode}
%
% \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%
  \caldate%
  \dates@subrange@end\dates@date%
  \dates@reg=\expandafter{\dates@subranges}%
  \edef\dates@subranges{%
    \the\dates@reg%
    \noexpand\delim{\the\dates@subrange@start}%
      {\the\dates@date}}%
  \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%
      \global\let\dates@init\dates@init@monthly@dom%
      \global\let\dates@increment\dates@increment@monthly@dom%
    \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%
  \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%
  \global\dates@date=\dates@subrange@start\relax%
  \caldate%
  \dates@init%
  \caldate%
  \ifdates@suppress@global%
  \else%
    \ifdates@suppress%
    \else%
%      \bgroup%
%      \dates@capsup%
        \dates@action%
%      \egroup%
    \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%
    \caldate%
    \ifdates@suppress@global%
    \else%
      \ifdates@suppress%
      \else%
        \dates@action%
      \fi%
    \fi%
  \else%
    \let\next\relax%
  \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{%
  \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}
%    \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}
%    \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{%
  \let\dates@init@monthly@dow@recurse\relax%
  \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{%
  \let\dates@init@monthly@dom@recurse\relax%
  \ifnum\dates@day>\dates@everymonth@day%
    \dates@next@month%
    \let\dates@init@monthly@dom@recurse\dates\init@monthly@dom%
  \else%
    \dates@day\dates@everymonth@day%
    \dates@fix%
  \fi%
  \dates@init@monthly@dom@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}
%    \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 {%
  \edef\dates@init{\csname#1\endcsname}%
  \edef\dates@increment{\csname#2\endcsname}%
  \@ifnextnparchar\enditall%
   {\bgroup%
      \makeatletter%
      \expandafter\dates@@@@read@@function\@gobble}%
   {\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 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%
        \multiply\dates@time@start by 60%
        \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%
      \dates@time@start=\dates@arg@a\relax%
      \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%
      \dates@time@end=\dates@arg@a\relax%
      \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)] \label{analyze} 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%
    \expandafter\csname#1#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:
%
% \begin{macrocode}
\def\daymac{%
  \global\let\dates@increment=\dates@increment@daily}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\othmac}
%
% "Other" will modify the effect of "every" to
% choose every other date within the range.  You
% can't choose the starting dates within the
% subrange --- but some automation is better than none. 
% 
%    \begin{macrocode}
\def\othmac{%
  \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}{\1stmac}
% \begin{macro}{\2ndmac}
% \begin{macro}{\3rdmac}
%
% These are just aliases of the macros above.
%
%    \begin{macrocode}
\expandafter\let\csname1stmac\endcsname=\firmac%
\expandafter\let\csname2ndmac\endcsname=\secmac%
\expandafter\let\csname3rdmac\endcsname=\thimac%
%    \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%
    \dates@month=0%
    \dates@day=0%
    \setyear{1900}%
  \fi%
  \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@increment\relax%
          \global\let\dates@init\dates@init@weekly%
          \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}
\bgroup
\newtoks\dates@reg
\dates@reg={}
\def\dates@capsdown{}
\def\dates@capsup{}
\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}%
  \dates@reg=\expandafter{%
    \dates@capsup\edef#1{\string#1}}%
  \xdef\dates@capsup{\the\dates@reg}%
  \let\next\dates@capsactive%
  \next}
\dates@capsactive%
  AAaBBbCCcDDdEEeFFfGGgHHhIIiJJjKKk%
  LLlMMmNNnOOoPPpQQqRRrSSsTTtUUuVVv%
  WWwXXxYYyZZz\end
\egroup
%    \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{%
      \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%
    \dates@month=1%
    \dates@day=1%
  \else%
    \advance\dates@month by 1%
    \dates@day=1%
  \fi%
  \dates@fix\caldate}
%    \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{%
 \dates@yearbase=-1%
 {\count0=\dates@year\divide\count0 by4%
 \multiply\count0 by4\relax%
 \ifnum\dates@year=\count0%
   \global\dates@catch=0%
 \else%
   \global\dates@catch=1%
 \fi}%
 \ifcase\dates@catch \leapyeartrue\or%
  \leapyearfalse\fi%
 {\count0=\dates@year\multiply\count0%
 by1461\advance\count0 by3%
 \divide\count0 by4%
 \global\dates@catch=\count0}%
 \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}%
 \dates@day=\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.
%
%    \begin{macrocode}
\def\dates@fix{%
 \ifnum\dates@month=0%
   \ifdates@requiremonth%
     \PackageError{dates}{Missing month}{%
       You need to specify a date for the month in this date entry.}%
   \else%
     \dates@month=1%
   \fi%
 \fi%
 \ifnum\dates@day=0%
   \ifdates@requireday%
     \PackageError{dates}{Missing day of the month}{%
       You need to specify a day of the month in this date entry.}%
   \else%
     \dates@day=1%
   \fi%
 \fi%
 \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%
   \dates@date=\dates@day{\advance\dates@month by-1%
    \monthdays%
    \advance\dates@date by\dates@day%
    \global\advance\dates@date by\dates@yearbase}%
 \fi}
%    \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".
%
%    \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{%
  \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%
  \ifcase\dates@weekd%
        \global\dates@dayname{Sunday}%
        \global\dates@shortweekday{Sun}%
    \or \global\dates@dayname{Monday}%
        \global\dates@shortweekday{Mon}%
    \or \global\dates@dayname{Tuesday}%
        \global\dates@shortweekday{Tue}%
    \or \global\dates@dayname{Wednesday}%
        \global\dates@shortweekday{Wed}%
    \or \global\dates@dayname{Thursday}%
        \global\dates@shortweekday{Thu}%
    \or \global\dates@dayname{Friday}%
        \global\dates@shortweekday{Fri}%
    \or \global\dates@dayname{Saturday}%
        \global\dates@shortweekday{Sat}%
  \fi}
%    \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\dates@month=0%
 \loop\monthdays\ifnum\dates@day<\dates@date%
 \global\advance\dates@month by1\repeat%
 {\advance\dates@month by-1\monthdays%
 \advance\dates@date by-\dates@day%
 \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".
%
%    \begin{macrocode}
\def\dates@monthname@get{%
  \ifcase\dates@month%
    \or \global\dates@monthname{January}%
        \global\dates@shortmonthname{Jan}%
        \global\dates@days=31\relax%
    \or \global\dates@monthname{February}%
        \global\dates@shortmonthname{Feb}%
        \ifleapyear%
          \global\dates@days=29\relax%
        \else%
          \global\dates@days=28\relax%
        \fi%
    \or \global\dates@monthname{March}%
        \global\dates@shortmonthname{Mar}%
        \global\dates@days=31\relax%
    \or \global\dates@monthname{April}%
        \global\dates@shortmonthname{Apr}%
        \global\dates@days=30\relax%
    \or \global\dates@monthname{May}%
        \global\dates@shortmonthname{May}%
        \global\dates@days=31\relax%
    \or \global\dates@monthname{June}%
        \global\dates@shortmonthname{Jun}%
        \global\dates@days=30\relax%
    \or \global\dates@monthname{July}%
        \global\dates@shortmonthname{Jul}%
        \global\dates@days=31\relax%
    \or \global\dates@monthname{August}%
        \global\dates@shortmonthname{Aug}%
        \global\dates@days=31\relax%
    \or \global\dates@monthname{September}%
        \global\dates@shortmonthname{Sep}%
        \global\dates@days=30\relax%
    \or \global\dates@monthname{October}%
        \global\dates@shortmonthname{Oct}%
        \global\dates@days=31\relax%
    \or \global\dates@monthname{November}%
        \global\dates@shortmonthname{Nov}%
        \global\dates@days=30\relax%
    \or \global\dates@monthname{December}%
        \global\dates@shortmonthname{Dec}%
        \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{{\count0=#1\mod7\dates@date\dates@weekd%
 \advance\count0 by-\dates@weekd\relax%
 \ifnum\count0<0\advance\count0 by7\fi%
 \global\advance\dates@date by\count0}}
%    \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%
 \advance\dates@date by\dates@timezone\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 = count0*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\count0%
 \multiply\count2 by\count0\relax%
 \multiply\count3 by\count0%
 \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}
%
% This initializes
% "\uselongtext" to the value selected by the user
% in the package calling "dates".
%    \begin{macrocode}
\def\dates@initialize@longtext{%
  \ifuselongtext%
    \def\dates@reset@longtext{%
      \longtexttrue}%
  \else%
    \def\dates@reset@longtext{%
      \longtextfalse}%
  \fi}
%    \end{macrocode}
%
% Before anything further is executed, the following registers
% and macros need to be in place.
%
%    \begin{macrocode}
\newcount\dates@year
\newcount\dates@timezone
\dates@timezone=0
\newcount\dates@catch
\newcount\dates@day
\newcount\dates@everymonth@day
\newcount\dates@month
\newcount\dates@date
\newcount\dates@one
\newcount\dates@two
\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\iflongtext
\longtexttrue
\newif\ifdates@requiremonth
\newif\ifdates@requireday
\newif\ifdates@suppress
\newif\ifdates@suppress@global
\newif\ifleapyear
\let\delim\relax
\def\enditall{END IT ALL}
\def\dates@empty{}
%</style>
%    \end{macrocode}
%
% \section{The Demo File}
%
%    \begin{macrocode}
%<*demo>
\documentclass{minimal}
\usepackage{dates}
\begin{document}

\makeatletter

%<demo>%
%<demo>% We invoke the \dateread command.
%<demo>%
\dateread
%<demo>%
%<demo>% We tell it to report a few details to the terminal.
%<demo>%
{\message{\theshorttext}%
 \message{\theday/\the\dates@month/\the\dates@year}%
 \ifx\thelongtext\dates@empty%
 \else%
   \message{\thelongtext}%
 \fi}
%<demo>%
%<demo>% The following are ranges.
%<demo>%
   december 10 1995 {^^JStart of First}
to jan     10 1996 {End of First}
   december 10 1996 {^^JStart of Second}
to jan     10 1997 {End of Second^^J}
%<demo>%
%<demo>% The following are specific dates (obviously)
%<demo>%
February 18 1997 {^^JFrank'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 {^^JFrank's Next Birthday But One}
%<demo>%
%<demo>% These are a couple of recursive dates.
%<demo>%
Every Monday {^^JMonday Coffee}
Every Third Tuesday {^^JMeeting}
%
%<demo>% Here is a sample function definition, which gives
%<demo>% the phases of the moon within the ranges.  The code
%<demo>% was ripped off from the calendar package for plain
%<demo>% TeX
%<demo>%

function \moonsinit \moonsincrement

 {
  \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}

%<demo>% Compute date for cycle quarter MOONNO

  \def\moondate{{\count0=\moonno
  \lin 202.126.369+0.\count0=\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}

%<demo>% 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 }

%<demo>% 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 }

%<demo>% Events for phases.
%<demo>% Uses PHASE (local).

  \def\phase{{\count0=\moonno
  \count1=\moonno
  \divide\count0 by4\multiply\count0 by4
  \advance\count1 by-\count0\relax
  \global\edef\themoon{\ifcase\count1
  New Moon\or First Quarter\or
  Full Moon\or Last Quarter\fi}}}

  \gdef\moonsinit{%
  \firstmoon
  \dates@month=12\dates@day=31\dates@fix\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}
%
%\iffalse
%    \begin{macrocode}
%<syntax>% \section{Date Syntax}
%<syntax>%
%<syntax>% \subsection{General Rules}
%<syntax>%
%<syntax>% The rules themselves are explained here first.  If you
%<syntax>% want to cut to the chase, have a look at the examples
%<syntax>% and experiment a bit with the demo file.  It's all
%<syntax>% pretty straightforward.
%<syntax>%
%<syntax>% The parser is indifferent to extra spaces and blank
%<syntax>% lines in dates.  It will read a string word by word,
%<syntax>% and classify each word as a time, a day of the month,
%<syntax>% the name of a month, a year or a special function.
%<syntax>% With two exceptions, strings beginning in a number must not mix numbers and
%<syntax>% other characters --- this will produce a low-level
%<syntax>% error from \TeX, and at the moment I can't think of
%<syntax>% an economical way of protecting against this.
%<syntax>%
%<syntax>% Any string
%<syntax>% beginning in a number is interpreted as either a
%<syntax>% time, a day of the month or a year.  A string
%<syntax>% containing a colon (the ":" character) is assumed
%<syntax>% to be a time of day.  "AM" and "PM" are not recognized;
%<syntax>% you should use 24-hour format when specifying
%<syntax>% times.  A numeric string containing a hyphen is assumed
%<syntax>% to be a range of times.  In this instance, a colon
%<syntax>% is not necessary if the time is given in whole-hours.
%<syntax>% Pure numeric strings are construed as a day of the month
%<syntax>% if less than 32, or as a year if greater than 31.
%<syntax>%
%<syntax>% Character strings are interpreted on the basis of their
%<syntax>% first three characters; the rest are ignored.  Case is
%<syntax>% also irrelevant.  Months and days of the week (used for
%<syntax>% defining recursive dates, described below) as well as certain
%<syntax>% special functions are specified as character strings.
%<syntax>% Any word that does not match an existing function
%<syntax>% will be ignored.
%<syntax>%
%<syntax>% Dates are always terminated by a short description
%<syntax>% of the date, which must be in curly braces.
%<syntax>% The description should contain plain text only;
%<syntax>% do not put macros (like "\LaTeX") here.
%<syntax>%
%<syntax>% Dates will be processed until "\dateread" encounters
%<syntax>% "\end{<"\meta{environment name}">}", or the string
%<syntax>% "\relax{}".  At the "\end" of an environment,
%<syntax>% the processing of the current date will be completed,
%<syntax>% and the "\end" will be executed.  "\relax{}" will
%<syntax>% cause processing to end silently without doing
%<syntax>% anything on the last item (which is the "\relax{}" itself).
%<syntax>%
%<syntax>% \subsection{Specific Dates}
%<syntax>%
%<syntax>% Applying the above rules, the following is a valid
%<syntax>% list of dates.  The use of "\dateread" is explained
%<syntax>% below.
%<syntax>%
%<syntax>% \begin{quote}
%<syntax>% \begin{verbatim}
%<syntax>% \begin{quote}
%<syntax>% \dateread{\message{\theshorttext}}
%<syntax>% Jan 1 1996{New Year's Day}
%<syntax>%      1    January 1996 at 10:00
%<syntax>%          {New Year Bash}"\\
%<syntax>% 1996
%<syntax>%     jan 1 8-20:30
%<syntax>%     {New Year Cleaning. Rats.}"
%<syntax>% \end{quote}
%<syntax>% \end{verbatim}
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% Note that the parser is indifferent to word order,
%<syntax>% and that commas should not be used to separate
%<syntax>% words.\footnote{In fact, commas do no harm if
%<syntax>% they follow a string of three or more letters, but
%<syntax>% it is best to keep things simple and clean.}
%<syntax>%
%<syntax>% \subsection{Recursive Dates}
%<syntax>%
%<syntax>% \subsubsection{Ranges}
%<syntax>%
%<syntax>% Any recursive dates (such as "Every" "Monday") must
%<syntax>% be preceded by one or more range specifications,
%<syntax>% which fix the time period or periods within which to
%<syntax>% recurse.
%<syntax>% A range is simply two specific dates separated by the
%<syntax>% word "to".  You may specify multiple ranges;
%<syntax>% effect will be given to each of them individually.
%<syntax>%
%<syntax>% The following is a valid range specification:
%<syntax>%
%<syntax>% \begin{quote}
%<syntax>% \begin{verbatim}
%<syntax>%    February  1 1996 {Start First Period}
%<syntax>% to April     1 1996 {End First Period}
%<syntax>%    November  3 1996 {Start Second Period}
%<syntax>% to December 24 1996 {End Second Period}
%<syntax>% \end{verbatim}
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% \subsubsection{Shorthand Dates}
%<syntax>%
%<syntax>% Three types of recursive date can be entered in a 
%<syntax>% human-readable syntax.  Entries of all types
%<syntax>% begin with the word "every".  To put an event
%<syntax>% on every occurence of a day of the week within
%<syntax>% a specified set of subranges, simply indicate the day
%<syntax>% of the week, followed by a short description
%<syntax>% in curly braces.
%<syntax>%
%<syntax>% \begin{quote}
%<syntax>% \begin{verbatim}
%<syntax>% Every Monday {Monday!}
%<syntax>% \end{verbatim}
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% To put an event at 14-day intervals, beginning
%<syntax>% with the first occurrence of a specified day
%<syntax>% of the week within each subrange, add the
%<syntax>% word "other".
%<syntax>%
%<syntax>% \begin{quote}
%<syntax>% \begin{verbatim}
%<syntax>% Every other Monday 7:00 {Monday Morning Exercise}
%<syntax>% \end{verbatim}
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% To place an event on the "N"th occurrence of
%<syntax>% a specified day of the week within each month, within
%<syntax>% subrange, add "first", "second" or "third".
%<syntax>%
%<syntax>% \begin{quote}
%<syntax>% \begin{verbatim}
%<syntax>% Every third Monday 8:00-9:00
%<syntax>%   {Monday Morning Meeting}
%<syntax>% \end{verbatim}
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% To place an event on the same day (as opposed to
%<syntax>% day of the week) in every month, just put the
%<syntax>% number of that day after "every":
%<syntax>%  
%<syntax>% \begin{quote}
%<syntax>% \begin{verbatim}
%<syntax>% Every 20 {Mortgage payment}
%<syntax>% \end{verbatim}
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% \subsubsection{Suppressing the Action}
%<syntax>%
%<syntax>% There are two ways of suppressing the user-defined action.
%<syntax>% To quickly comment out an entry, put the word "rem" in
%<syntax>% front of it.  The date will be read, but the action
%<syntax>% in the argument to "\dateread" will not be performed.
%<syntax>% This can be used, for example, to suppress the appearance
%<syntax>% of a range in the output text.
%<syntax>%
%<syntax>% The second method uses a toggle, and is meant for use by
%<syntax>% style authors.  Setting:
%<syntax>%
%<syntax>% \begin{quote}
%<syntax>% "\dates@suppress@globaltrue"
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% \noindent will cause the user action to be suppressed
%<syntax>% throughout the invocation of "\dateread".  In order for
%<syntax>% the action to be performed on the next invocation,
%<syntax>% the toggle must be set to "false" in the external
%<syntax>% code that calls the parser.
%<syntax>%
%<syntax>% \subsubsection{Functions}
%<syntax>%
%<syntax>% It is possible to specify dates within the subranges
%<syntax>% using an arbitrary formula.  Entries of this type
%<syntax>% begin with the word "function".  This is followed
%<syntax>% by two control strings, a block of \LaTeX{} code in
%<syntax>% curly braces, and the usual short description, also in 
%<syntax>% curly braces.
%<syntax>%
%<syntax>% The first control string is the name of a
%<syntax>% user-defined macro that will find the position
%<syntax>% of the first desired date after the start of the
%<syntax>% range.  The second is the name of a macro to
%<syntax>% use in incrementing afterward.  The block of
%<syntax>% \LaTeX{} code contains the definitions of these
%<syntax>% and any subsidiary macros.
%<syntax>%
%<syntax>% The following will place an entry on every date within
%<syntax>% the specified subranges.
%<syntax>%
%<syntax>% \begin{quote}
%<syntax>% \begin{verbatim}
%<syntax>% Function \myinit \myincrement
%<syntax>%  {\def\myinit{%
%<syntax>%    \dates@date=\dates@subrange@start}
%<syntax>%   \def\myincrement{%
%<syntax>%    \advance\dates@date by 1\relax}
%<syntax>%  }
%<syntax>%  {A Day}
%<syntax>% \end{verbatim}
%<syntax>% \end{quote}
%<syntax>%
%<syntax>% See the code commentary section of the Dates package for information
%<syntax>% on macros that can be used for manipulating dates.
%    \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}}
   }

\preamble

This file is part of the Dates package,
Copyright (C) 1996, 1997 Frank Bennett, Jr.
All rights reserved.
------------------------------------------
This file is provided for demonstration purposes; feel free
to edit it in any way whatsoever.
------------------------------------------



\endpreamble

\postamble
\endpostamble

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

\preamble
\endpreamble

\let\WritePreamble\@gobble
\let\WritePostamble\@gobble

\generate{\file{datesynt.tex}{\from{dates.dtx}{syntax}}
   }

\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