[R] isdst

[Prof Brian Ripley]

On Thu, 6 Oct 2005, Omar Lakkis wrote:

> Can someone, please, explain the difference is results below (notice
> the isdst value)

Timezones.  (That is carefully documented on the help page for 
as.POSIXlt.)

>> unlist(as.POSIXlt('2005-7-1'))
>  sec   min  hour  mday   mon  year  wday  yday isdst
>    0     0     0     1     6   105     5   181     1

This is midnight on 2005-07-01 in your timezone, which presumably does 
have DST and it was in force then.

>> unlist(as.POSIXlt(as.Date('2005-7-1')))
>  sec   min  hour  mday   mon  year  wday  yday isdst
>    0     0     0     1     6   105     5   181     0

This is midnight on 2005-07-01 in UTC (which does not have DST).

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595