This is one of InLOC's direct properties.

validityStart expresses the start date of the validity of the learning outcome or competence definition or structure. It is the other end of the validity interval from validityEnd.

This must not be confused with the date at which an individual may become qualified or licensed to do something connected with the LOC.

It must be given in W3C DTF.

The Dublin Core term "valid" is envisaged as an ISO time interval, but that is possibly not very well understood generally, and the position of InLOC is that it is better to make the start and end dates of a valid period explicit.