Detecting Browser Time Zone with Rails

I recently revisited the problem of detecting browser time zone because I wanted to try the new time zone functionality in Rails 2.1. I found this post from Dave Johnson. To my disappointment this was the same solution Spongecell used in the personal calendar 3 years ago.

I wanted a simpler solution: one that doesn’t require a js cookie library, nor around filters, nor a UI with a combo box with 100s of time zone choices.

The solution presented is to send browser info using jquery and then storing the time zone in the session for use in all subsequent requests.

in the view (this is haml), this can be in your layout on all pages:

    - unless @time_zone

      = javascript_tag "$.get('/controller/time_zone',

      'offset_minutes':(-1 * (new Date()).getTimezoneOffset())})"

in the controller:

 before_filter :init_time_zone
  #sets the time zone for this request if a session time zone exists
  #if it doesn't the default is UTC

  def init_time_zone

    @time_zone = ActiveSupport::TimeZone[session[:time_zone_name]] if session[:time_zone_name]

    Time.zone = @time_zone.name if @time_zone

  end

  #this receives browser info from a jquery request and stores 

  #time zone info in the session
  def time_zone

    offset_seconds = params[:offset_minutes].to_i * 60

    @time_zone = ActiveSupport::TimeZone[offset_seconds]

    @time_zone = ActiveSupport::TimeZone["UTC"] unless @time_zone

    session[:time_zone_name] = @time_zone.name if @time_zone

    render :text => "success"

  end

in the formatter:
  def format_time(t)

    return "" unless t

    return t.in_time_zone.strftime('%Y-%m-%d %H:%M:%S %Z')

  end

Look how simple that is! I choose to default the time zone to UTC if one cannot be determined on the first attempt. Now the formatter will output all the UTC times you have in your db or anywhere in the user’s browser’s time zone.

If there is a better solution in Rails please let me know. We ‘ll see if this solution works for daylight saving time.