R34 has validity period
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...).
LCSH February 20 to March 19 2012 (F34) R34 has validity period February 20 to March 19 2012 (E52) DDC 19 (F34) R34 has validity period 1979 to 1989 (E52)