5 CFR § 831.651 - Commencing and terminating dates of survivor annuities.
(a) Except as provided in paragraph (b) of this section, current spouse annuities, former spouse annuities, children's survivor annuities, and survivor annuities for beneficiaries of insurable interest annuities under CSRS begin to accrue on the day after death of the employee, Member, or retiree.
(b)
(1) A current spouse annuity begins to accrue—
(i) Upon attainment of age 50 when, under section 12 of the Civil Service Retirement Act Amendments of February 29, 1948, the annuity is deferred until age 50; or
(ii) Upon OPM's receipt of a claim for an annuity authorized for unremarried widows and widowers by section 2 of the Civil Service Retirement Act Amendments of June 25, 1958, 72 Stat. 218.
(2) A former spouse annuity begins to accrue—
(i) For annuities under § 831.683, on the later of the day after date of death of the retiree or the first day of the second month after the date the application for annuity is received in OPM; or
(ii) For annuities when a former spouse annuity is authorized by court order under section 8341(h) of title 5, United States Code, on the later of the day after the date of death of the employee, Member, or retiree or the first day of the second month after the court order awarding the former spouse annuity and the supporting documentation required by § 838.721 or § 838.1005 of this chapter are received in OPM.
(c) A survivor annuity terminates at the end of the month preceding death or any other terminating event.
(d) A current spouse annuity terminated for reasons other than death may be restored under conditions defined in sections 8341(e)(2) and 8341(g) of title 5, United States Code.
(e) A survivor annuity accrues on a daily basis, one-thirtieth of the monthly rate constituting the daily rate. An annuity does not accrue for the 31st day of any month, except in the initial month if the survivor's (of a deceased employee) annuity commences on the 31st day. For accrual purposes, the last day of a 28-day month constitutes 3 days and the last day of a 29-day month constitutes 2 days.
(f) Initial cost-of-living increases on current and former spouse annuities, and annuities to beneficiaries of insurable interest annuities are prorated under section 8340(c) of title 5, United States Code.