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MathGroup Archive 2010

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AbsoluteTime and Daylight Saving Time

  • To: mathgroup at smc.vnet.net
  • Subject: [mg111519] AbsoluteTime and Daylight Saving Time
  • From: David Skulsky <edskulsky at gmail.com>
  • Date: Wed, 4 Aug 2010 05:48:14 -0400 (EDT)

The Mathematica documentation states that "AbsoluteTime[] uses
whatever date and time have been set on your computer system.  It
performs no corrections for time zones, daylight saving time, etc."
This statement confuses me.  When I execute the following commands on
my machine (Mathematica 7 running under Mac OS 10.6.4) it appears that
AbsoluteTime is accounting for DST since the two AbsoluteTime commands
return the same value for times that differ by 1 hour (at the DST
transition).

datestr = {"Day", "MonthNameShort", "Year", "Hour24", "Minute",
   "SecondExact"};

AbsoluteTime[{"13 Mar 2016 02:00:00.000", datestr}]
3666826800

AbsoluteTime[{"13 Mar 2016 03:00:00.000", datestr}]
3666826800

So I thought I'd try to specify the time zone using the TimeZone->0
option in the AbsoluteTime command, but that didn't appear to solve
the problem (i.e., both calls to AbsoluteTime still return the same
value, though it differs from the previous calls to AbsoluteTime by
the offset associated with my local time zone).  I thought that
specifying the time zone would remove any compensation for DST, since
DST seems to be accounted for by adjusting the time zone.

Can somebody help me understand what's going on?

Thanks,

David Skulsky




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