isValid(): Boolean;
The isValid method of the Date primitive type returns true if the receiver is a valid date. This method returns false if the date is invalid.
This method also returns false for dates outside the valid internal representation range of 24th November -4713 through 31st December 1465072 Gregorian.
The code fragment in the following example shows the use of the isValid method.
if (day.String & "/" & month.String & "/" & year.String).Date.isValid then
calendar.date.setDate(day, month, year);
else
calendar.date.setDate(1, month, year);
endif;