This post originated from an RSS feed registered with Ruby Buzz by rwdaigle. Original Post: What's New in Edge Rails: Easier Timezones Feed Title: Ryan's Scraps Feed URL: http://feeds.feedburner.com/RyansScraps Feed Description: Ryan Daigle's various technically inclined rants along w/ the "What's new in Edge Rails" series. Latest Ruby Buzz Posts Latest Ruby Buzz Posts by rwdaigle Latest Posts From Ryan's Scraps

The days of forcing time-zone support into your Rails apps with not one, but two plugins are over. It would appear that Rails now has its own way of dealing with timezones via a custom implementation (though it’s still based on the tzinfo gem).

Here’s the deal. You can now create an ActiveSupport::TimeWithZone from an instance of a UTC-based Time and then switch between time-zones at will:

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# Use a UTC time as your base
utc = Time.utc(2000, 1, 1, 0) #=> Sat Jan 01 00:00:00 UTC 2000

# And set the initial timezone
time = ActiveSupport::TimeWithZone.new(utc, TimeZone['Eastern Time (US & Canada)'])
  #=> 1999-12-31 19:00:00 -0500

# And now you can display the time in different timezones without changing the time itself
time.in_time_zone('London') #=> 2000-01-01 00:00:00 -0000
time #=> 1999-12-31 19:00:00 -0500

# Or if you do want to change the timezone
time.change_time_zone('London')
time #=> 2000-01-01 00:00:00 -0000

So how can we use this new timezone support in the real world – as in our Rails apps where you let users define their own timezone? We can do this using an around filter to set a timezone class variable, much in the same way you’re used to doing:

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class ApplicationController < ActionController::Base

  around_filter :set_timezone

  def set_timezone
    # current_user.time_zone #=> 'London'
    before, Time.zone = Time.zone, Time.get_zone(current_user.time_zone)
    yield
  ensure
      Time.zone = before
  end
end

Now your controller actions and views can access the time in the current (user’s) timezone:

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<!-- current_user.registered_at is a UTC datetime -->
<%= TimeWithZone.new(current_user.registered_at).in_current_time_zone %>

One could easily imagine using a view helper to reduce the verbosity of the above statement:

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def current_time(utc)
  TimeWithZone.new(utc).in_current_time_zone
end

So you can now do this in your views:

<%= current_time(current_user.registered_at) %>

You can also create a TimeWithZone instance from the local time if you’re not dealing with UTC instances:

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# Set the initial time based on the local timezone
time = ActiveSupport::TimeWithZone.new(nil, TimeZone['London'], london_time)

At the end of the day you’ve got a timezone solution built into Rails that avoids needless dependencies and establishes a common practice for multi-timezone applications.

This was a pretty fragmented post – let me know if you spot any discrepancies or blatant errors.

tags: ruby, rubyonrails