Question: what is the difference between rr and yy in oracle?
Answer: YY allows you to retrieve just two digits of a year, for example, the 99 in 1999. The other digits (19) are automatically assigned to the current century. RR converts two-digit years into four-digit years by rounding. Essentially, your first example will assume that 81 is 2081 whereas the RR one assumes 1981.