R help - Oct 2011 - any way to convert back to DateTime class when "accidental" conversion to numeric?

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]]

This game you are playing is quite dangerous, and I recommend that you avoid
this assiduously. Look at the lubricate library or use the chron or Date
classes. Timestamps are rather poor candidates for numeric operations, and the
vagaries of timezones are quite a headache.
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Mike Williamson <this.is.mvw@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@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.


	[[alternative HTML version deleted]]

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?