On 2/8/2011 11:47 AM, David Winsemius wrote:
On Feb 8, 2011, at 10:31 AM, Manuel Gimond wrote:
Converting date strings that range between Mar-14-2010 2:00 and
Mar-14-2010 2:59 (inclusive) to date objects (POSIX) returns a NA
entity:
strptime("3/14/2010 2:00",format="%m/%d/%Y %H:%M")
[1] "2010-03-14 02:00:00"
This looks fine, however other functions such as plot see a NA object
instead:
is.na(strptime("3/14/2010 2:00",format="%m/%d/%Y %H:%M"))
[1] TRUE
I've processed an entire range of dates for 2010 and have only come
across this problem for the aforementioned date ranges. For instance,
the following dates work fine:
is.na(strptime("3/14/2010 3:00",format="%m/%d/%Y %H:%M"))
[1] FALSE
is.na(strptime("10/14/2010 23:00",format="%m/%d/%Y %H:%M"))
[1] FALSE
which is what I would expect for ALL dates.
Could this be a bug with POSIX or strptime?
More likely it has to do with "daylight savings time".
Thanks David, DST was indeed the problem. The data I'm working with is
in local standard time. Adding the tz="EST" fixed the problem, e.g.:
is.na(strptime("3/14/2010 2:00",format="%m/%d/%Y %H:%M",tz="EST"))
[1] FALSE
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