http://hl7.org/fhir/StructureDefinition/uncertainPeriod|5.2.0

Used to express an uncertain date(+time) value by specifying an allowed or observed upper and lower bound.

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