[Openmcl-devel] Universal time question

[Phil]

Gary,

Thanks for the info and I see the problem in my math.  While truncating 
the time, I forgot to factor in the time zone: I needed to truncate the 
h:m:s and then add back the local time zone delta to get back to midnight.

Thanks,
Phil

Gary Byers wrote:
> Note that GET-UNIVERSAL-TIME returns the number of seconds since 
> January 1,1900 GMT, and that DECODE-UNIVERSAL-TIME decodes a universal
> time relative to the local time zone (unless DECODE-UNIVERSAL-TIME
> is given an explicit time zone as a second argument.)
> 
> So (as of a few minutes ago ...):
> 
> ? (setf mytime1 (get-universal-time))
> 3355113528
> ?  (setf mytime2 (* (floor (/ mytime1 86400)) 86400))
> 3355084800
> ?  (decode-universal-time mytime2 0)
> 0
> 0
> 0
> 27
> 4
> 2006
> 3		; Hmm.  Is it Wednesday or Thursday ?
> NIL
> 0
> 
> You were getting the same answer, but DECODE-UNIVERSAL-TIME was presenting
> it in your local time zone (and doing DST handling).
> 
> Aside from the question of what day of the week it is at midnight, I'm
> aware of a couple of bugs in 1.0 related to universal time functions:
> 
> - ENCODE-UNIVERSAL-TIME doesn't handle 2-digit years correctly (so 05
> is "2001 years ago", rather than "last year")
> 
> - functions that accept a timezone argument probably don't accept the
> full range of legal values (I've seen some test suite failures, but
> don't remember the exact details.)
>