18.104.22.168.1 Semantic definition
The IfcDuration identifies a quantity of time (or a "length" of an event occurring in time).
This lexical representation for IfcDataTime is PnYnMnDTnHnMnS, where nY represents the number of years, nM the number of months, nD the number of days, 'T' is the date/time separator, nH the number of hours, nM the number of minutes and nS the number of seconds. The number of seconds can include decimal digits to arbitrary precision.
22.214.171.124.2 Formal representation
TYPE IfcDuration = STRING; END_TYPE;