[R] Difference between times

[Rui Barradas]

Hello,

The reason why is that you've misspelled CET (not CEST)

 > dt1 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz = 
"CEST")
Warning messages:
1: In strptime(x, format, tz = tz) : unknown timezone 'CEST'
2: In as.POSIXct.POSIXlt(as.POSIXlt(x, tz, ...), tz, ...) :
   unknown timezone 'CEST'
 > dt2 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz = "GMT")
 > dt1 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz = "CET")
 > dt1-dt2
Time difference of -2 hours


Hope this helps,

Rui Barradas

Em 18-04-2014 17:13, Nicola Sturaro Sommacal escreveu:
> Hi.
>
> I am new to POSIX and I'd like to understand the reason of this difference.
>
> dt1 = as.POSIXct("2014-03-29 09.00", format="%Y-%m-%d %H.%M")
> dt2 = as.POSIXct("2014-03-30 09.00", format="%Y-%m-%d %H.%M")
> dt2-dt1
>
>> dt1[1] "2014-03-29 09:00:00 CET"> dt2[1] "2014-03-30 09:00:00 CEST"> dt2-dt1
>
> Time difference of 23 hours
>
> This is right, because on Mar 31 at 2 PM we jump directly to 3PM, DST.
>
> On the contrary, I don't understand the following:
>
> dt1 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz = "CEST")
> dt2 = as.POSIXct("2014-04-18 09.00", format="%Y-%m-%d %H.%M", tz = "GMT")
>
>> dt1[1] "2014-04-18 09:00:00 CEST"> dt2[1] "2014-04-18 09:00:00 GMT"> dt1-dt2Time difference of 0 secs
>
>
> I should expected a time difference of 2 hours, as CEST is GMT+2.
>
> Anyone can help me?
>
> Thank you,
> Nicola
>
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