[H-GEN] time in C/C++

[Anthony Towns]

On Wed, Dec 29, 1999 at 05:02:04PM +1000, Paul Gearon wrote:
> Well I can't comment on leap-seconds (as I don't know when they occur), but
> in terms of determining time differences between consecutive days, then
> difftime is fine.

As long as you take into account things like 00:00:01 1/Jan/2000 -
23:59:59 31/Dec/1999 = 2 seconds, but is probably a whole day as far as
you're concerned.

Converting all your units to whole multiples of 86400 is probably good
enough. In C, something like:

	days = timet / 86400; /* discard the remainder */
or	norm_timet = timet - (timet % 86400);
or	norm_timet = days * 86400;

is probably fine. (with diff = days2 - days1; or
diff = (norm_timet2 - norm_timet1) / 86400)

> (unless leap seconds are a concern?  BTW, when ARE they?)

Leap seconds are probably never a concern: your watches/clocks/timers
probably have bigger errors anyway.

They happen when some timekeepers somewhere decide we need one, and get
tacked onto the end of a month sometime. ntp will keep your clock up to
date.

Cheers,
aj

-- 
Anthony Towns <aj at humbug.org.au> <http://azure.humbug.org.au/~aj/>
I don't speak for anyone save myself. GPG encrypted mail preferred.

 ``The thing is: trying to be too generic is EVIL. It's stupid, it 
        results in slower code, and it results in more bugs.''
                                        -- Linus Torvalds
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