For purposes of determining the pro rata share of annuity, survivor annuity or lump-sum payable to a former spouse, the following shall be considered creditable service—

(a) The entire period of a principal's approved leave without pay during full-time service with an organization composed primarily of Government employees irrespective of whether the principal elects to make payments to the Fund for this service;

(b) The entire period of Government service for which a principal received a refund of retirement contributions which he/she has not repaid unless the former spouse received under §19.13 a portion of the (lump-sum) refund or unless a spousal agreement or court order provided that no portion of the refund be paid to the former spouse; and

(c) All creditable service including service in excess of 35 years.

The period covered by the credit for unused sick leave is not creditable for this purpose.