From: Jason Green <news AT jgreen4 DOT fsnet DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: strftime: Need Help with Time Offsets
Date: Tue, 26 Dec 2000 23:36:05 +0000
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JT Williams <jeffw AT darwin DOT sfbr DOT org> wrote:

> -: If someone has the time to figure out the calculation for week numbers
> -: (%V) from any supplied date, that would help.
> 
> Take a look in "Astronomical Algorithms", by Jean Meeus.

Erm, the week no's required for strftime() have nothing to do with the
position of the planets. ;-)

(IOW, If that reference is appropriate please can you expand it.)

This is what needs to be figured out:

: In this system, weeks begin on a Monday and week 1 of the year is the   
: week that includes January 4th, which is also the week that includes   
: the first Thursday of the year, and is also the first week that   
: contains at least four days in the year.  If the first Monday of   
: January is the 2nd, 3rd, or 4th, the preceding days are part of the  
: last week of the preceding year; thus, for Saturday 2nd January 1999,  
: %G is replaced by 1998 and %V is replaced by 53.  If December 29th,  
: 30th, or 31st is a Monday, it and any following days are part of week  
: 1 of the following year.  Thus, for Tuesday 30th December 1997, %G is  
: replaced by 1998 and %V is replaced by 1. 

The week number, %V as defined above, needs to be calculated from the
date fields of a struct tm.