http://hl7.org/fhir/StructureDefinition/openEHR-exposureDate|4.0.1

Record of the date and/or time of the first exposure to the Substance for this Reaction Event.
typedestination
baseDefinitionhttp://hl7.org/fhir/StructureDefinition/Extension
typehttp://hl7.org/fhir/StructureDefinition/Extension
Extension.value[x].typehttp://hl7.org/fhir/StructureDefinition/dateTime