Some of your dates are displayed BST and some GMT.
High probablilty your dates span the break between summer time and regular
time when
certain hours do not exist.  (in the US we go from 0200 directly to 0301 in
the spring when we move
from standard time to daylight time).  0230 would therefore be displayed as
NA.

You will need to take control of the time zone, probably by forcing GMT at
all times.

On Sun, May 27, 2012 at 3:56 PM, Des Callaghan <des.callaghan@ecostudy.co.uk
> wrote:

> Hello Forum,
>
>
>
> I have a problem with the strptime function. With the 'data1' dataset below
> it works fine, but with the 'data2' dataset something goes wrong (see final
> line below). Both data1 and data2 are in exactly the same original format,
> the only difference is that they span different dates. Please help, since
> it
> is driving me nuts! Many thanks.
>
>
>
> Best wishes,
>
> Des
>
> -
>
> > data1=read.table("data1.txt",header=T,sep="\t")
>
> > datetime1=strptime(data1$Date, "%a %b %d %H:%M:%S %Y") #example line from
> data1 'Tue Aug 16 03:00:01 2011'
>
> > summary(datetime1)
>
>                     Min.                   1st Qu.
> Median                      Mean
>
> "2011-08-15 21:00:01 BST" "2011-10-08 01:00:01 BST" "2011-11-30 05:00:01
> GMT" "2011-11-30 04:38:47 GMT"
>
>                  3rd Qu.                      Max.
>
> "2012-01-22 09:00:01 GMT" "2012-03-15 13:00:01 GMT"
>
> > min(datetime1)
>
> [1] "2011-08-15 21:00:01 BST"
>
> > data2=read.table("data2.txt",header=T,sep="\t")
>
> > datetime2=strptime(data2$Date, "%a %b %d %H:%M:%S %Y") #example line from
> data2 'Sun Nov 27 13:07:01 2011'
>
> > summary(datetime2)
>
>                     Min.                   1st Qu.
> Median                      Mean
>
> "2011-11-27 01:07:01 GMT" "2012-01-09 20:07:01 GMT" "2012-02-22 15:07:01
> GMT" "2012-02-22 15:26:16 GMT"
>
>                  3rd Qu.                      Max.
>
> "2012-04-06 12:07:01 BST" "2012-05-20 07:07:01 BST"
>
> > min(datetime2)
>
> [1] NA
>
>
>
>
>
>
>
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>

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