Re: Calender program

From: Dr John Stockton (spam_at_merlyn.demon.co.uk)
Date: 01/31/05

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    Date: Sun, 30 Jan 2005 23:35:52 +0000

    JRS: In article <32F59E6E.5675@alcatel.no>, dated Mon, 3 Feb 1997
    09:14:38, seen in news:comp.lang.pascal.borland, Sven Pran
    <Sven.Pran@alcatel.no> posted :

    >A very handsome algorithm valid for any year in the Gregorian calendar
    >is:
    >
    >Function DOW(y,m,d : word)word;
    >begin
    >if m < 3
    > then
    > begin
    > m := m+12;
    > y := y-1;
    > end;
    > DOW := (((3*m + 3) div 5) + 2*m + d + y + (y div 4) - (y div 100) + (y
    >div 400)) mod 7;
    >end;
    >
    >The answer is 0 for Monday through 6 for Sunday.
    >
    >I hope I got the typo correct! The algorithm showed up here a couple of
    >months ago,
    >I am sorry I don't remember the author, so I can't give him proper
    >credit.

    I don't know who wrote the Pascal; but the algorithm is substantially
    that of Zeller <URL:http://www.merlyn.demon.co.uk/zeller-c.htm> . It
    can be improved by following Zeller more closely and putting 2*m inside
    div 5, merging to 13*m. Needs a final +1 for ISO 8601 numbers.

    NG line reduced.
      

    -- 
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