Date-Routines for C/UNIX ? HELP

[Christopher Lott]

In article <207600039 at s.cs.uiuc.edu> mccaugh at s.cs.uiuc.edu writes:
>
> I tried mailing to Mathias, but no luck...anyway, here (at least) is the
> C code for day-of-week given the date as MMDDYYYY:
>......

I was sent this function some time ago.  The author's name appears below.
Seems to work very well, and is nice and short. 

I have not tested it extensively.  If someone can tell me more about the
below-referenced "Zeller" function, I'd appreciate it.



   >From pats at cup.portal.com Thu Jun 29 10:27:56 1989
   From: pats at cup.portal.com (Pat T Shea)
   Newsgroups: comp.sys.ibm.pc
   Subject: Re: calendar code
   Date: 29 Jun 89 00:19:58 GMT
   Organization: The Portal System (TM)
   
   'think this is what ur looking for. . . . /pats.
    
   /***********************************************************************
    *
    *          int  dmy2dow( int iDay, int iMon, int iYear ) - This is my
    *             implementation of the Zeller function.  It takes day/
    *             month/year and returns the day of the week as an int
    *             with Sunday being 0.....etc.
    *  /pats @Psi!
    *  11/05/85
    ******/
   int dmy2dow( int day, int mon, int year )
   {
      int adj_mo, adj_yr, cent, cent_yrs;
    
      adj_mo = ( mon > 2 ) ? mon - 2 : mon + 10;
      adj_yr = ( mon > 2 ) ? year    : year - 1;
      cent = adj_yr / 100;
      cent_yrs = adj_yr % 100;
      return((((( 13 * adj_mo - 1 ) / 5 ) + day + cent_yrs +
                ( cent_yrs / 4 ) + ( cent / 4 ) - 2 * cent + 77 ) % 7 ));
   }

Hope this is useful to someone.

chris...
cml at tove.umd.edu    Computer Science Dept, U. Maryland at College Park
		    4122 A.V.W.  301-454-8711	<standard disclaimers>