[R] How to convert SPSS date data to dates?

[Prof Brian Ripley]

On Thu, 16 Feb 2006, Peter Dalgaard wrote:

> "Jonathan Williams" <jonathan.williams at pharmacology.oxford.ac.uk> writes:
>
>> Dear R Helpers,
>>
>> I have imported an SPSS file that contains date data.
>> The data appear in R in a numeric format, as follows:
>>
>> 10485849600 10477641600 10561104000 10562745600 etc.
>>
>> I'd be extremely grateful if someone could tell me
>> how to make these numbers into comprehensible dates!
>
>> c(10485849600,10477641600,10561104000,10562745600)+ISOdate(1582,10,14)
> [1] "1915-01-26 13:00:00 CET" "1914-10-23 13:00:00 CET"
> [3] "1917-06-15 13:00:00 CET" "1917-07-04 13:00:00 CET"
>
> Does this look right? (If you don't want the times, use as.Date).
>
> BTW: There's a strange asymmetry:
>
>> ISOdate(1582,10,14)+
>> c(10485849600,10477641600,10561104000,10562745600)
> [1] "1915-01-26 12:00:00 GMT" "1914-10-23 12:00:00 GMT"
> [3] "1917-06-15 12:00:00 GMT" "1917-07-04 12:00:00 GMT"
>
> (have we seen this before?).

Yes, and the second is correct.  Timezones are taken from the lhs in
+.POSIXt.  (That could probably now safely be changed.)

-- 
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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