The TimeFrame constructor function is particularly simple and a TimeFrame with default attributes is created as follows:
INCLUDE 'AST_PAR' INTEGER TIMEFRAME, STATUS STATUS = 0 ... TIMEFRAME = AST_TIMEFRAME( ' ', STATUS )
Such a TimeFrame would represent the default coordinate system which is
Modified Julian Date (with the usual units of days) in the International
Atomic Time (TAI) time scale.
AST A Library for Handling World Coordinate Systems in Astronomy