time_t

Stuart D. Gathman stuart at gathman.org
Thu Jul 17 12:46:20 EDT 2008


Nathan Buchanan wrote:
> I agree that the 00:00 timestamp is a bug, but the 12:00Z or 10:01:00Z
> simply works around the bug for 90% of the use cases. From the perspective
>   
Not only that, but if you force the time of day in each timestamp to 
12:00Z, then you no longer have a timestamp, but a complicated and 
difficult to use date type.  You can't even subtract these ersatz "date" 
types to get days between dates.  (No dividing by 24*60*60 doesn't work 
- don't forget DST, etc).

There is *far* less code overall to just store dates (ideally a day 
number of some sort) where you want dates (i.e. where you would force 
the TOD to 12:00), and store timestamps where you need timestamps (stock 
prices, etc).  I've been dealing with this issue for 30 years, and seen 
the same mistake made over and over.  Similar to trying to do accounting 
with binary floating point.  Yes, you can make it work by rounding every 
other line of code.  But it is butt ugly, slow, and error prone.  And 
usually doesn't actually work in any given application (invoice totals 
sometimes off by a penny).



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