On Fri, 11 Aug 2000, Nathan Wiger wrote:
> > Adding support for (modified) Julian Date will be much more
> > generic and remove dependency on unix epoch with little
> > extra code.
>
> To me, the real question is which date() should we use:
>
> $date = date $seconds_since_epoch; # uses time()
> $date = date $modified_julian_date; # non-Unix
This would be fine so long as time() returned an MJD rather than seconds
(or another function was supplied for returning the current time).
I was not really proposing that seconds should be dropped just that MJD is
an alternative (the other difference is that unix time is an integer and
MJD has to be a double).
>
> If we can make it work, the second one seems a lot more
> platform-independent. After all, the epoch has no meaning to those on
> Macs, PCs, or BeOS machines (except maybe historical trivia).
>
> Are we agreed that date() should now be based on Julian date? Here's the
> advantages:
>
> 1. Unix-independent (yeah, I love Unix, but...)
>
> 2. Allows easy date arithmetic (complex -> module)
>
It should be possible to do date arithmetic with the seconds returned by
time()
$tomorrow = time() + 24*60*60;
so the second point is not really an advantage. The main issue is that
date() has a method for returning some number such as this that will allow
for easy date arithmetic. MJD has a more generic feel.
> And here's the disadvantages:
>
> 1. Unix time() no longer the basis for date
>
> Although that really isn't a disadvantage, just a difference.
Indeed.
--
Tim Jenness
JCMT software engineer/Support scientist
http://www.jach.hawaii.edu/~timj
