http://hl7.org/fhir/StructureDefinition/Age|4.0.1

Base StructureDefinition for Age Type: A duration of time during which an organism (or a process) has existed.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Quantity
typehttp://hl7.org/fhir/StructureDefinition/Age
Age.binding.valueSethttp://hl7.org/fhir/ValueSet/age-units