[R] any way to convert back to DateTime class when "accidental" conversion to numeric?

[Prof Brian Ripley]

A more portable way (that function only works in some versions of R) 
is

as.POSIXct(1317857320, origin="1970-01-01")

possibly with a 'tz' argument if you need to restore the timezone.

On Wed, 5 Oct 2011, jim holtman wrote:

> Here is what I use:
>
> unix2POSIXct(1317857320)
> [1] "2011-10-05 19:28:40 EDT"
>
>
> unix2POSIXct  <-  function (time) structure(time, class = c("POSIXt",
> "POSIXct"))
>
>
> On Wed, Oct 5, 2011 at 7:38 PM, Mike Williamson <this.is.mvw at gmail.com> wrote:
>> Hi,
>>
>>    In short, I would like to know if there is any way to convert a numeric
>> into a date, similar to how strptime() can convert a string to a date time
>> class?
>>
>>    There are some functions, etc. which don't work well with dates, and
>> tend to force them into numerics.  I understand that the number it spits
>> back is the number of seconds since the beginning of 1970 (see the first few
>> sentences of the "Details" portion of ?DateTimeClasses).
>>    However, it's a bit of a hassle to convert that by hand.  I can create a
>> function to do this, and it isn't so hard, but I found it hard to believe
>> such a function didn't already exist, so I wanted to ask the community.
>>
>>    As an example, today (Oct 5th 2011 at approximately 4:30pm, Pacific
>> time) is approximately 1317857320 as a numeric, but I would like to know how
>> to go from that number back to the "2011-10-05 16:28:39 PDT" date time class
>> which originally generated it.
>>
>>                        Thanks!
>>                              Mike
>>
>> ---
>> XKCD <http://www.xkcd.com>
>>
>>        [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help at 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
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
>
> -- 
> Jim Holtman
> Data Munger Guru
>
> What is the problem that you are trying to solve?
>
> ______________________________________________
> R-help at 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
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
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