[R] ISOdate returns incorrect date?

[Gabor Grothendieck]

Based on the discussion so far, the 1950 issue is due to the 
timezone and Prof. Riley has established that the 1900 issue
is a coding error in printing dates (but not in ISOdate, itself, 
or in the representation of POSIXct dates).

I assume that the 1900 was found by just playing around but if your
data actually does go that far back then note that neither of 
the above two issues will affect you if you use chron:

> require(chron)
> chron( paste(3,16,c(1900,1950),sep="/"), out.format="year-m-d")
[1] 1900-Mar-16 1950-Mar-16




--- 
Date: Wed, 19 Nov 2003 17:27:19 +0100 
From: Heiko Schaefer <heiko.schaefer at swissrisk.com>
To: <r-help at stat.math.ethz.ch> 
Subject: RE: [R] ISOdate returns incorrect date? 

 
 

It starts on the 1st of March 1900 to go wrong .... I feel better now
that somebody
Else these the same effect ;-)

-----Original Message-----
From: Simon Fear [mailto:Simon.Fear at synequanon.com] 
Sent: Mittwoch, 19. November 2003 17:17
To: ggrothendieck at myway.com; heiko.schaefer at swissrisk.com;
r-help at stat.math.ethz.ch
Subject: RE: [R] ISOdate returns incorrect date?


Well, I live only a few seconds away from GMT and I also get

> ISOdate(1900,6,16,tz="")
[1] "1900-06-15 12:00:00 GMT Daylight Time"

15th, not 16th.

Was 1900 a strange leap year? I certainly haven't tested thoroughly but
note this:

> ISOdate(1900,2,16,tz="")
[1] "1900-02-16 12:00:00 GMT Standard Time"
# 16th OK in February
> ISOdate(1900,3,16,tz="")
[1] "1900-03-15 12:00:00 GMT Standard Time"
# wrong for March

Using today's release of rw181beta (up to date or what?) 
on Win 98 (oh well).

> -----Original Message-----
> From: Gabor Grothendieck [mailto:ggrothendieck at myway.com]
> Sent: 19 November 2003 16:06
> To: heiko.schaefer at swissrisk.com; r-help at stat.math.ethz.ch
> Subject: RE: [R] ISOdate returns incorrect date?
> 
> 
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> ________________________________________________________________ 
> 
> 
> 
> ISOdate works, by default, in the GMT timezone. Try:
> 
> ISOdate(1900,6,16,tz="")
> ISOdate(1950,6,16,tz="")
> 
> If you don't need timezones and don't want to worry about them you can

> alternately use the chron library for your dates and times.
> 
> ---
> Date: Wed, 19 Nov 2003 14:58:24 +0100
> From: Heiko Schaefer <heiko.schaefer at swissrisk.com>
> To: <r-help at stat.math.ethz.ch> 
> Subject: [R] ISOdate returns incorrect date? 
> 
> 
> 
> 
> Dear all,
> 
> I have found the following (for me) incomprehensible behaviour of 
> ISOdate (POSIXct):
> > ISOdate(1900,6,16)
> [1] "1900-06-15 14:00:00 Westeuropdische Sommerzeit"
> > ISOdate(1950,6,16)
> [1] "1950-06-16 14:00:00 Westeuropdische Sommerzeit"
> 
> Note that in the first case I get the 15th of June back, not
> the 16th as
> I would have expected!
> This happened under R-1.7.1 on both windows and linux.
> 
> I would greatly appreciate your comments,
> 
> Heiko
> 
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Simon Fear 
Senior Statistician 
Syne qua non Ltd 
Tel: +44 (0) 1379 644449 
Fax: +44 (0) 1379 644445 
email: Simon.Fear at synequanon.com 
web: http://www.synequanon.com 

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