http://hl7.org/fhir/StructureDefinition/patient-birthTime|4.0.1

The time of day that the Patient was born. This includes the date to ensure that the timezone information can be communicated effectively.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/dateTime