zone_utc?

# File lib/time.rb, line 151
    def zone_utc?(zone)
      # * +0000
      #   In RFC 2822, +0000 indicate a time zone at Universal Time.
      #   Europe/Lisbon is "a time zone at Universal Time" in Winter.
      #   Atlantic/Reykjavik is "a time zone at Universal Time".
      #   Africa/Dakar is "a time zone at Universal Time".
      #   So +0000 is a local time such as Europe/London, etc.
      # * GMT
      #   GMT is used as a time zone abbreviation in Europe/London,
      #   Africa/Dakar, etc.
      #   So it is a local time.
      #
      # * -0000, -00:00
      #   In RFC 2822, -0000 the date-time contains no information about the
      #   local time zone.
      #   In RFC 3339, -00:00 is used for the time in UTC is known,
      #   but the offset to local time is unknown.
      #   They are not appropriate for specific time zone such as
      #   Europe/London because time zone neutral,
      #   So -00:00 and -0000 are treated as UTC.
      if /\A(?:-00:00|-0000|-00|UTC|Z|UT)\z/ =~ zone
        true
      else
        false
      end
    end