5 CFR §843.304

1. (a)A current or former spouse annuity under this subpart commences on the day after the death of the person on whose service the annuity is based.
2. (b)A current or former spouse annuity under this subpart terminates on the last day of the month before the current or former spouse remarries before age 55 or dies.
3. (c)A current spouse annuity under this subpart terminated for reasons other than death may be restored under § 843.305.
4. (d)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.