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From: moorer@jacobs.CS.ORST.EDU (Rocky Moore)
Newsgroups: comp.lang.c
Subject: Re: Day of week algorithm wanted for "C"
Message-ID: <13902@orstcs.CS.ORST.EDU>
Date: 20 Nov 89 15:54:29 GMT
References: <1031@icus.islp.ny.us>
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Reply-To: moorer@jacobs.CS.ORST.EDU.UUCP (Rocky Moore)
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Organization: Oregon State University - CS - Corvallis Oregon
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In article <1031@icus.islp.ny.us> lenny@icus.islp.ny.us (Lenny Tropiano) writes:
>I need a function that accepts a month, a day, and a year ... and returns
>the day-of-the-week (ie. Sunday, Monday, etc..)

Here is a little piece of code I pulled out of the time routine I use.  It will
return a value 0-6 where 0=Sunday, 1=Monday, ect...

--- CUT HERE ---

/* Find and return day of week (0-6) */

int day_of_week(int year, int month, int day)
{
     int offsets[13] = { 0,0,3,3,6,1,4,6,2,5,7,3,5 };
     int dw;

     dw=6+year+((year+3)/4)+offsets[month]+day;
     if( ((year%4) ==0) && (month > 2)) dw++;
     if( (year==0) && (month < 3)) dw++;
     dw=(dw%7);
     return(dw);
}

--- END ---

This should handle what you want.  Hope it helps.

Rocky Moore     moorer@jacobs.cs.orst.edu