Validate Timezones in Ruby on Rails

Rails makes it too simple to allow users to specify their timezone. All you have to do is add the following to your form:

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# ..
<%= f.time_zone_select :time_zone, ActiveSupport::TimeZone.us_zones %>
# ..

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# ..
field :time_zone, :type => String
# ..

Now you can see a very nice select element with all the timezones the world has to offer. In the above example, the US timezones will show before the rest of the world. But what do you do to validate the timezones? You just have to drop the below in to your model.

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# ..
validates_inclusion_of :time_zone, :in => ActiveSupport::TimeZone.zones_map { |m| m.name }, :message => "is not a valid Time Zone"
# ..

Simple!!