Your OS is? I cannot reproduce this on any of mine.
Sone OSes do not support dates before 1970, which would explain the
difference. R then has to guess when summer time ended in 1969, and I
suspect something is happening inconsistently.
Also, "EST" is not a real-world POSIX timezone and may well not be
implemented fully.
On Mon, 17 Oct 2005, Omar Lakkis wrote:
> Can someone, please, explain the difference in as.POSIXct results
> before 1970 and on and after 1970 as illustrated below.
>
> After 1970, the use of 'EST' or "EST+5EDT' as the timezone
does not
> affect the result of asPOSIXct, but before 1970 on 10/28 the results
> are different.
>
>> as.POSIXct('1970-10-29', tz='EST')+1
> [1] "1970-10-29 00:00:01 EST"
>> as.POSIXct('1970-10-29', tz='EST+5EDT')+1
> [1] "1970-10-29 00:00:01 EST"
>
>> as.POSIXct('1969-10-29', tz='EST')+1
> [1] "1969-10-29 00:00:01 EST"
>> as.POSIXct('1969-10-29', tz='EST+5EDT')+1
> [1] "1969-10-28 23:00:01 EST"
>
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--
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)
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