# File lib/et-orbi.rb, line 387
    def get_offset_tzone(str)

      m = str.match(/\A([+-][0-1]?[0-9]):?([0-5][0-9])?\z/) rescue nil
        #
        # On Windows, the real encoding could be something other than UTF-8,
        # and make the match fail
        #
      return nil unless m

      tz = custom_tzs[str]
      return tz if tz

      hr = m[1].to_i
      mn = m[2].to_i

      hr = nil if hr.abs > 11
      hr = nil if mn > 59
      mn = -mn if hr && hr < 0

      hr ?
        custom_tzs[str] = create_offset_tzone(hr * 3600 + mn * 60, str) :
        nil
    end