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From: mccaugh@s.cs.uiuc.edu
Newsgroups: comp.lang.c
Subject: Re: Date-Routines for C/UNIX ? HELP
Message-ID: <207600041@s.cs.uiuc.edu>
Date: 12 Sep 89 06:02:00 GMT
References: <298@nixsin.UUCP>
Lines: 27
Nf-ID: #R:nixsin.UUCP:298:s.cs.uiuc.edu:207600041:000:1056
Nf-From: s.cs.uiuc.edu!mccaugh    Sep 12 01:02:00 1989


 I'm sorry if my code (in the first comment) is less than neat: I did
 test it out extensively so it at least works, but could be more efficient.
 In particular, the line assigning to variable lp_yrs should read:

          lp_yrs  =  (yyyy-1)/4 - 492;

 I tried modifying that line but it was already networked.

 Not sure what was meant by requesting 'previous day' or 'next day': were
 these requests for a new date or for the name of said day? In any event,
 just take the code I gave for day-of-week and add/subtract 86400 (= #(secs)
 per day) to value 'secs' to get a new duration in seconds, then proceed
 from there.

 The easiest part is checking date-validity, as the call to 'localtime()'
 returns info to check against the given date. Upon its return, we can
 first query if UNIX returns a date consistent with our own:

     /*  check:  dd == tp->tm_mday    */
     /*  check:  mm == tp->tm_mon     */
     /*  check:  yyyy == tp->tm_year  */

 and only then should the day-of-week be printed out.
 Again, hope this helps.

 Scott McCaughrin