On Tue, 10 Mar 2009, lbrag...@gmail.com wrote:
Full_Name: Luca Braglia
Version: 2.8
OS: Windows
Submission from: (NULL) (85.18.136.110)
From ?as.POSIXct
## SPSS dates (R-help 2006-02-17)
z <- c(10485849600, 10477641600, 10561104000, 10562745600)
as.Date(as.POSIXct(z, origin="1582-10-14", tz="GMT"))
^^
It should be 15 (Gregorian calendar adoption day, when SPSS starts to count
seconds behind dates) . With 14, I used a .sav dataset imported with read.spss,
and after as.Date(as.POSIXct()) I got (obviously)
R.date = SPSS.date - 1
Hmm, from the SPSS 'Programming and Data Management' guide:
'Internally, dates and date/times are stored as the number of seconds
from October 14, 1582, and times are stored as the number of seconds
from midnight.'
Now, they might just mean the last second of October 14, 1582, but
that is not how many other people have read this (including those in
the thread mentioned).
Wikipedia for example describes October 15, 1582 as the first day of
the Gregorian calendar, which makes 1582-10-14 day zero.
Given that this is an example only, I don't think we should change it
without quite strong evidence that SPSS's documentation is misleading.
Bye (and thank you for givin'us R)
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Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
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