gml:TimePositionType

temporal.xsd

Direct representation of a temporal position. 
      Indeterminate time values are also allowed, as described in ISO 19108. The indeterminatePosition 
      attribute can be used alone or it can qualify a specific value for temporal position (e.g. before 
      2002-12, after 1019624400). 
      For time values that identify position within a calendar, the calendarEraName attribute provides 
      the name of the calendar era to which the date is referenced (e.g. the Meiji era of the Japanese calendar).