Calculates the number of full years between the two dates as an integer constant. Full year difference between 31/12/2004 and 01/01/2005 is 0
FULL_YEARS (start, end)
Two attributes of the Date type or date constants or calculations producing date
Number: the count of full years between the two dates.
IF FULL_YEARS (Account.OpeningDate, Account.ClosingDate) = 5 THEN ...