Primitive type 'ts'
A quantity specifying a point on the axis of natural time. A point in time is most often represented as a calendar expression.
A date, date-time or partial date (e.g. just year or year + month). If hours and minutes are specified, a UTC offset SHALL be populated. The format is a union of the schema types gYear, gYearMonth, date and dateTime. Seconds must be provided due to schema type constraints but may be zero-filled and may be ignored. Dates SHALL be valid dates.
UTC offset is allowed for dates and partial dates
All FHIR elements must have a @value or children
hasValue() or (children().count() > id.count())
unique id for the element within a resource (for internal references)
Must have either extensions or value[x], not both