From ripley at stats.ox.ac.uk  Mon Nov 27 14:46:12 2006
From: ripley at stats.ox.ac.uk (ripley at stats.ox.ac.uk)
Date: Mon, 27 Nov 2006 14:46:12 +0100 (CET)
Subject: [Rd] as.Date: conversion pb from POSIXct (PR#9386)
Message-ID: <20061127134612.0FDE55730D@slim.kubism.ku.dk>

You have not told us your timezone, but this seems to be as documented if 
you are in CET.  The help page says

      The 'as.Date' methods accept character strings, factors, logical
      'NA' and objects of classes '"POSIXlt"' and '"POSIXct"'.  (The
      last are converted to days by ignoring the time after midnight in
      the representation of the time in UTC.)
                                     ^^^^^^

Probably as.POSIXct(strptime("1994-01-24","%Y-%m-%d") is 1994-01-23 23:00 
in UTC in your timezone.

On Mon, 27 Nov 2006, xiao.gang.fan1 at free.fr wrote:

> Full_Name: Xiao Gang FAN
> Version: 2.4.0
> OS: Windows
> Submission from: (NULL) (159.50.101.9)
>
>
>> library(chron)

Irrelevant.

>> as.Date(as.POSIXct(strptime("1994-01-24","%Y-%m-%d")))
> [1] "1994-01-23"

Not in my timezone.

-- 
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



[Rd] as.Date: conversion pb from POSIXct (PR#9386)
ripley at stats.ox.ac.uk