Monkey patch ActiveSupport::TimeZone to fix TZInfo::AmbiguousTime errors

monkey_patches.rb

# put this file in config/initializers/monkey_patches.rb
require 'monkey_patches/active_support/time_zone'

time_zone.rb

# put this in lib/monkey_patches/active_support/time_zone.rb
module MonkeyPatches
  module ActiveSupport
    module TimeZone
      extend ::ActiveSupport::Concern

      included do
        alias_method_chain :period_for_local, :ambiguous_handling
      end

      # This monkey patch fixes exceptions like this one:
      # TZInfo::AmbiguousTime: 2014-10-26 01:00:12 UTC is an ambiguous local time.
      # They happen to appear when code like `3.days.ago` or `Time.zone.parse('some ambiguous date here')` is used,
      # i.e. when some local time point can be translated into more than 1 points of time in UTC time, like it's
      # happened in Europe/Moscow on October 26, 2014 when time from 01:00:00 till 01:59:59 went twice:
      # 01:00:00 MSK +04:00 -> 01:59:59 MSK +04:00
      # 01:59:59 MSK +04:00 -> 01:00:00 MSK +03:00
      # 01:00:00 MSK +03:00 -> 02:00:00 MSK +04:00
      # This change is permanent, so no daylight saving time (DST) is involved here
      # See https://github.com/tzinfo/tzinfo/issues/32 for discussion
      #
      # Most of the time TZInfo resolves ambiguous dates by itself, but when it can't we have to choose it manually
      # via supplied block, so take the earlier date by default
      def period_for_local_with_ambiguous_handling(time, dst=true)
        tzinfo.period_for_local(time, dst) { |results| results.first }
      end
    end
  end
end

ActiveSupport::TimeZone.send :include, MonkeyPatches::ActiveSupport::TimeZone

time_zone_spec.rb

# put this file in spec/lib/monkey_patches/active_support/time_zone_spec.rb
require 'spec_helper'
require 'timecop'

describe MonkeyPatches::ActiveSupport::TimeZone do
  describe 'ambigious time bug' do
    # I could reproduce this bug only on Rails 3.x
    it 'n.days.ago should not throw exception' do
      Timecop.travel(Time.zone.parse('27.10.2014 1:30:00 MSK +03:00')) do
        expect { 1.day.ago }.not_to raise_error
      end
    end

    it 'Time.zone.parse should not throw exception' do
      expect { Time.zone.parse('26.10.2014 1:30:00') }.not_to raise_error
    end
  end
end

I am using this patch only while running specs (since only my specs are affected) so I'll put it in spec/support and require it in my rails_helper.rb. I hope it will help me get rid of those flaky tests, thanks