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: Thu, 11 Jan 2001 21:56:52 +0000
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Esa A E Peuha <peuha AT cc DOT helsinki DOT fi> wrote:

> > Erm, sorry, this is not obvious to me.  Although that's probably more
> > to do with damage suffered staring at date maths code. ;-)
> 
> No wonder. :-)  It's all pretty simple once you really understand it,
> but it can be mind-boggling before that. 

For a student of mathematics perhaps. ;-)

> > I put your code into functions.  Unfortunately, it sometimes gets the
> > week number wrong where week 52/53 overlaps into the new year.
> 
> So it does.  That's because I made a silly mistake (see below).
> 
> >       /* day belongs to last week of previous year */
> >       return number_of_week (t->tm_wday,
> >                              t->tm_yday +
> >                              ((isleap(t->tm_year + TM_YEAR_BASE)) ?
> >                               366:365));
> 
> This, of course, needs to add the number of days in the previous year,
> so it should test for isleap(t->tm_year + TM_YEAR_BASE - 1). 

Yep that fixes it, thanks.  I'll put this together with what I have
already and post a patch to the djgpp-workers list.

> BTW, why
> is there an extra set of parentheses around isleap(...)?

Only because I generally prefer to place parentheses around the
condition just as if it were an `if' or `while' statement, I think
that makes the code easier to read.