% This macro source file is from the four volume series
% "TeX in Practice" by Stephan von Bechtolsheim, published
% 1993 by Springer-Verlag, New York.
% Copyright 1993 Stephan von Bechtolsheim.
% No warranty or liability is assumed.
% This macro may be copied freely if no fees other than
% media cost or shipping charges are charged and as long
% as this copyright and the following source code itself
% is not changed. Please see the series for further information.
%
% Version: 1.0
% Date: May 1, 1993
%
%
% This source code is documented in 26.16, p. III-381.
% Original source in file "macros6.TEX", starting line 1098.
\wlog{L: "arbday.tip" ["macros6.TEX," l. 1098, p. III-381]}%
% This file DOES belong to format "texip."
\InputD{legdate.tip}
\InputD{dateofw.tip}
\InputD{imodn.tip}
\InputD{nextday.tip}
\InputD{numdyr.tip}
\InputD{prmonth.tip}
\InputD{earliest.tip}
\InputD{doloop.tip}
\catcode`\@ = 11
\newcount\@YearTemp
\newcount\@YearTop
\newcount\@MonthTemp
\newcount\@MonthTop
\newcount\@TempAD
\def\ArbitraryDayOfWeek #1#2#3#4{%
    \CheckDate{#1}{#2}{#3}%
    #4 = \DayOfWeekOfEarliestDate
    \@YearTop = #1\relax
    \advance\@YearTop by -1
    \DoLoop{\@YearTemp}{\EarliestYearDate}{1}{\@YearTop}{%
        \NumberOfDaysInYear{\@YearTemp}{\@TempAD}%
        \advance #4 by \@TempAD
    }%
    \IModN{#4}{7}{#4}%
    \@MonthTop = #2\relax
    \advance\@MonthTop by -1
    \DoLoop{\@MonthTemp}{1}{1}{\@MonthTop}{%
        \NumberOfDaysInMonth{#1}{\@MonthTemp}{\@TempAD}%
        \advance #4 by \@TempAD
    }%
    \IModN{#4}{7}{#4}%
    \advance #4 by #3\relax
    \advance #4 by -1
    \IModN{#4}{7}{#4}%
}
\catcode`\@ = 12