5 CFR §843.408

1. (a)An annuity under this subpart—
   1. (1)Commences on the day after the retiree or employee dies;
   2. (2)Commences or resumes on the first day of the month in which the child later becomes or again becomes a student as described by § 843.313, if any lump sum paid is returned to the Civil Service Retirement Fund; or
   3. (3)Commences or resumes on the first day of the month in which the child later becomes or again becomes incapable of self-support because of a mental or physical disability incurred before age 18 (or a later recurrence of such disability), if any lump sum is returned to the Fund.
2. (b)An annuity under this subpart terminates on the last day of the month before the child—
   1. (1)Becomes 18 years of age unless he or she is a student as described in § 843.410 or is incapable of self-support;
   2. (2)Becomes capable of self-support after becoming 18 years of age unless he or she is a student as described in § 843.410;
   3. (3)Becomes 22 years of age if he or she is a student as described in § 843.410 and—
      1. (i)Capable of self-support; or
      2. (ii)Incapable of self-support because of a mental or physical disability incurred after age 18;
   4. (4)Ceases to be such a student as described in § 843.410 after becoming 18 years of age unless he or she is incapable of self-support; or
   5. (5)Dies or marries.
3. (c)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.