http://hl7.org/fhir/StructureDefinition/date|5.0.0

date Type: A date or partial date (e.g. just year or year + month). There is no UTC offset. The format is a union of the schema types gYear, gYearMonth and date. Dates SHALL be valid dates.
NameFlagsCardTypeDescription & Constraints
date
0..*Primitive Type date
 
value
0..1http://hl7.org/fhirpath/System.DatePrimitive value for date