The IfcDate identifies a particular calendar day, expressed by year, calendar month and day in month. It is expressed by a string value following a particular lexical representation.
The lexical representation for IfcDate is the YYYY-MM-DD, where YYYY represents the calendar year, MM the ordinal number of the calendar month, and DD the ordinal number of the day within the calendar month. No left truncation is allowed. An optional following time zone qualifier is allowed. To accommodate year values outside the range from 0001 to 9999, additional digits can be added to the left of this representation and a preceding "-" sign is allowed.
TYPE IfcDate = STRING; END_TYPE;