Section 838.242 - Computing lengths of service(a)(1) The smallest unit of time that OPM will calculate in computing a formula in a court order is a month, even where the court order directs OPM to make a more precise calculation.(2) If the court order states a formula using a specified simple or decimal fraction other than twelfth parts of a year, OPM will use the specified number to perform simple mathematical computations.(b) Unused sick leave is counted as "creditable service" on the date of separation for an immediate CSRS or FERS annuity. The unused sick leave of a phased retiree is counted as "creditable service" on the date of separation of the phased retiree to enter full retirement status. Unused sick leave is not apportioned over the time when earned.57 FR 33574, July 29, 1992, as amended at 79 FR 46626 , Aug. 8, 2014