http://hl7.org/fhir/StructureDefinition/artifact-effectivePeriod|5.2.0

When the artifact is expected to be used.

element_id	types
Extension
Extension.url	uri
Extension.value[x]	Period
Extension
Extension.id	http://hl7.org/fhirpath/System.String
Extension.extension	Extension
Extension.url	uri
Extension.value[x]	Period