Date changed FHIR Extension

{
    "resourceType":"StructureDefinition",
    "id":"date-changed",
    "url":"https://openmrs.org/fhir/StructureDefinition/date-changed",
    "name":"date-changed",
    "status":"draft",
    "kind":"primitive-type",
    "abstract":false,
    "contextType":"datatype",
    "type":"Extension",
    "baseDefinition":"http://hl7.org/fhir/StructureDefinition/Extension",
    "derivation":"constraint",
    "differential":{
        "element": [
            {
                "id":"Extension.url",
                "path":"Extension.url",
                "fixedUri":"https://openmrs.org/fhir/StructureDefinition/date-changed"
            },
            {
                "id":"Extension.value[x]:valueDateTime",
                "path":"Extension.valueDateTime",
                "sliceName":"valueDateTime",
                "type": [
                    {
                        "code":"dateTime"
                    }
                ]
            },
            {
                "id":"valueDateTime:valueDateTime.id",
                "path":"Extension.valueDateTime.id",
                "max":"0"
            }
        ]
    }
}