POSIX and summer savings time
On Wed, 6 Dec 2006, Derek Eder wrote:
I have a time stamp in UTC (GMT) time:
format(ISOdatetime(1970,1,1,0,0,0)+1165398135729/1000,"%Y-%m-%d
%H:%M:%OS3") "2006-12-06 09:42:18.823" (note millisecond accuracy, but not relevant to question here)
But it is the wrong answer, and not what my system gives.
Now, this time stamp actually "happened" at local (Swedish) time one hour later (10:42).
So you need to tell R that it was in UTC, which is what the 'tz' argument is for:
(z <- ISOdatetime(1970,1,1,0,0,0, tz="UTC")+1165398135729/1000)
[1] "2006-12-06 09:42:15 UTC"
format(z, "%Y-%m-%d %H:%M:%OS3", tz="CET")
[1] "2006-12-06 10:42:15.729"
Regarding summer/winter adjustments in time ("spring forward, fall
back"): Is there a way of automatically recovering the local time
adjustments for a given date? E.g., a date/time in springtime = GMT +2
, else GMT +1
Is the above not enough? You can unpick it if you want to get the shift.
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595