Convert UTC to local time in Rails 3

ruby-on-rails ruby ruby-on-rails-3 timezone activesupport
Marc-André Lafortune picture Marc-André Lafortune · Mar 14, 2011 · Viewed 104k times · Source

I'm having trouble converting a UTC Time or TimeWithZone to local time in Rails 3.

Say moment is some Time variable in UTC (e.g. moment = Time.now.utc). How do I convert moment to my time zone, taking care of DST (i.e. using EST/EDT)?

More precisely, I'd like to printout "Monday March 14, 9 AM" if the time correspond to this morning 9 AM EDT and "Monday March 7, 9 AM" if the time was 9 AM EST last monday.

Hopefully there's another way?

Edit: I first thought that "EDT" should be a recognized timezone, but "EDT" is not an actual timezone, more like the state of a timezone. For instance it would not make any sense to ask for Time.utc(2011,1,1).in_time_zone("EDT"). It is a bit confusing, as "EST" is an actual timezone, used in a few places that do not use Daylight savings time and are (UTC-5) yearlong.

Answer

Dylan Markow picture Dylan Markow · Mar 14, 2011

Time#localtime will give you the time in the current time zone of the machine running the code:

> moment = Time.now.utc
  => 2011-03-14 15:15:58 UTC 
> moment.localtime
  => 2011-03-14 08:15:58 -0700

Update: If you want to conver to specific time zones rather than your own timezone, you're on the right track. However, instead of worrying about EST vs EDT, just pass in the general Eastern Time zone -- it will know based on the day whether it is EDT or EST:

> Time.now.utc.in_time_zone("Eastern Time (US & Canada)")
  => Mon, 14 Mar 2011 11:21:05 EDT -04:00 
> (Time.now.utc + 10.months).in_time_zone("Eastern Time (US & Canada)")
  => Sat, 14 Jan 2012 10:21:18 EST -05:00

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