Scope note: This property associates an instance of F34 KOS with the instance of E52 Time-Span describing the period for which the particular KOS Expression was regarded as valid by its maintainers. Each change of validity status of a nomen use statement within a KOS should be associated with a release change of the KOS. The individual time-span of a validity state of a nomen would be the union of the time-spans of the KOS in which the Nomen was declared to have the particular validity status (provisional, accepted, obsolete etc...). Examples: - LCSH February 20 to March 19 2012 (F34) R34 has validity period February 20 to March 19 2012 (E52) - DDC 19 (F34) has validity period 1979 to 1989 (E52) Subproperty of: Out of CRM Scope?: Validity periods of plans point to future?