The create date/time of a value set compose is not supported in either the base ValueSet resource, nor in an extension. This element is required to maintain the original creation date for the compose versus the resource. .

The create date is specific to the compose.

Description: Date the compose was created.

URL = http://hl7.org/fhir/StructureDefinition/valueset-compose-creationdate

See row 33 here:  https://confluence.hl7.org/display/VOC/Resource+element+list