Forum: Ruby on Rails Yet Another Time Zone Question

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Randall (Guest)
on 2009-05-12 11:56
(Received via mailing list)
Seems like there should be an easy solution to this problem, yet I
can't seem to find one.

Here is the issue:
How do you assign a time zone to a Time object that results from a
parsed date/time string?

Example:
- I receive a date time string from a date picker widget that does not
include time zone info (i.e. "Mon May 11 18:24:37 2009").
- Time zone for this date is known and may be different than what's
local to the user
- date/time is stored in the DB as unix time (i.e. 1242075962)
- time zone is stored in the DB in tz format i(i.e. 'America/
New_York')
- I would like to be able to take a given date with its known time
zone and calculate the equivalent unix time value.

>> now = Time.now
=> Mon May 11 18:24:37 -0400 2009
>> now.to_i
=> 1242080677


>> parsed = DateTime.parse("Mon May 11 18:24:37 2009")
=> Mon, 11 May 2009 18:24:37 +0000
>> parsed.to_time
=> Mon May 11 18:24:37 UTC 2009
>> parsed.to_time.to_i
=> 1242066277
>> Time.at 1242066277
=> Mon May 11 14:24:37 -0400 2009

It seems there should be a way to append the time zone to the string
before it is parsed or to associate the parsed time with a time zone
(without converting the time to the zone), however I can't seem to
find an answer.

Any help would be greatly appreciated
Jeremy Olliver (Guest)
on 2009-05-13 02:32
(Received via mailing list)
Hi,

The time zone is encoded in the string at the end e.g

Mon, 11 May 2009 18:24:37 +1200
Is in a time zone that's +12 (12 hours ahead of utc)
DateTime.parse or Time.parse will read this correctly.

So what you're doing is using a js date picker that gives you a string
like "Mon May 11 18:24:37 2009"
You just need to append the time zone difference to "Mon May 11
18:24:37 2009 +1200" etc before parsing.

I handle storing dates in the db a little differently than you, but if
you know what you're doing don't worry about changing that part.
I usually store dates in the db in utc format (I think you can
configure this in environment.rb from memory), and you can easily set
the user's timezone in a filter in application controller
Time.zone = user.time_zone
which will handle all of the conversions for you.

Cheers,
Jeremy
Randall (Guest)
on 2009-05-13 23:34
(Received via mailing list)
Thanks Jeremy!
Rick D. (Guest)
on 2009-05-18 23:12
(Received via mailing list)
On Tue, May 12, 2009 at 6:31 PM, Jeremy Olliver
<removed_email_address@domain.invalid> wrote:
>> include time zone info (i.e. "Mon May 11 18:24:37 2009").
>> - Time zone for this date is known and may be different than what's
>> local to the user
>> - date/time is stored in the DB as unix time (i.e. 1242075962)
>> - time zone is stored in the DB in tz format i(i.e. 'America/
>> New_York')
>> - I would like to be able to take a given date with its known time
>> zone and calculate the equivalent unix time value.
...
>>
>> It seems there should be a way to append the time zone to the string
>> before it is parsed or to associate the parsed time with a time zone
>> (without converting the time to the zone), however I can't seem to
>> find an answer.
>>>

> The time zone is encoded in the string at the end e.g
>
> Mon, 11 May 2009 18:24:37 +1200
> Is in a time zone that's +12 (12 hours ahead of utc)
> DateTime.parse or Time.parse will read this correctly.
>
> So what you're doing is using a js date picker that gives you a string
> like "Mon May 11 18:24:37 2009"
> You just need to append the time zone difference to "Mon May 11
> 18:24:37 2009 +1200" etc before parsing.

Careful here,  there's a diference between a time zone like
"America/New_York" and a time zone offset
http://www.w3.org/TR/timezone/
>
> I handle storing dates in the db a little differently than you, but if
> you know what you're doing don't worry about changing that part.
> I usually store dates in the db in utc format (I think you can
> configure this in environment.rb from memory), and you can easily set
> the user's timezone in a filter in application controller
> Time.zone = user.time_zone
> which will handle all of the conversions for you.

Or to convert to an arbitrary timezone

Time.at(unix_time).in_timezone('America/New_York")

--
Rick DeNatale

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