R help - Nov 2008 - Unexpected behavior of difftime in relationship to daylight savings time

Colleagues,

I just encountered some unexpected behavior of difftime in  
relationship to the change from daylight savings to standard time.  My  
understanding is that DST and ST take effect at 2AM.  However, the  
code below suggests that R (version 2.8.0 in OS X) implements the  
change at 2:16AM:

Expected:
> > difftime("2008-11-02 02:01:00", "2008-11-02
00:59:00")
> Time difference of 2.033333 hours
> > difftime("2008-11-02 01:16:00", "2008-11-02
01:15:00")
> Time difference of 1 mins
> > difftime("2008-11-02 01:18:00", "2008-11-02
01:17:00")
> Time difference of 1 mins
Not expected:
> > difftime("2008-11-02 01:17:00", "2008-11-02
01:16:00")
> Time difference of 1.016667 hours
Can anyone explain this?

Dennis


Dennis Fisher MD
P < (The "P Less Than" Company)
Phone: 1-866-PLessThan (1-866-753-7784)
Fax: 1-415-564-2220
www.PLessThan.com


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