This code system http://terminology.hl7.org/CodeSystem/v3-PeriodicIntervalOfTimeAbbreviation defines many codes, but they are not represented here

 <status value="retired"/> <date value="2017-07-31"/> <publisher value="Health Level 7"/> <contact> <name value="Health Level Seven"/> </contact> <caseSensitive value="true"/> <content value="not-present"/> </CodeSystem>