Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!psuvax1!flee
From: flee@shire.cs.psu.edu (Felix Lee)
Newsgroups: comp.lang.c
Subject: Re: Day of week routine
Message-ID: <FLEE.89May22191959@shire.cs.psu.edu>
Date: 22 May 89 23:20:00 GMT
References: <234@zeek.UUCP> <322@xdos.UUCP>
Sender: news@psuvax1.cs.psu.edu
Distribution: usa
Organization: Penn State University Computer Science
Lines: 15
In-reply-to: doug@xdos.UUCP's message of 22 May 89 14:37:21 GMT

In article <322@xdos.UUCP>,
   doug@xdos.UUCP (Doug Merritt) writes:
>Try this:
>	((year * 1.25) + (day-of-the-year) + constant) modulo 7

Using a strict interpretation of (day-of-the-year), you should use
(year + (year-1)/4) instead of (year * 1.25).

For the Gregorian calendar, try this instead:
	year + (year-1)/4 - (year-1)/100 + (year-1)/400.

Note that not all countries adopted the Gregorian calendar at the
same time.  (Japan was quite late, something like 19th century?)
--
Felix Lee	flee@shire.cs.psu.edu	*!psuvax1!shire!flee