10 U.S.C. § 1253

(a) General Rule .— Unless retired or separated earlier, each regular commissioned officer of the Army, Navy, Air Force, Marine Corps, or Space Force serving in a general or flag officer grade shall be retired on the first day of the month following the month in which the officer becomes 64 years of age. (b) Exception for Officers Serving in O– 9 and O– 10 Positions .— In the case of an officer serving in a position that carries a grade above major general or rear admiral, the retirement under subsection (a) of that officer may be deferred— (1) by the President, but such a deferment may not extend beyond the first day of the month following the month in which the officer becomes 68 years of age; or (2) by the Secretary of Defense, but such a deferment may not extend beyond the first day of the month following the month in which the officer becomes 66 years of age. (c) Deferred Retirement of Chaplains .— (1) The Secretary of the military department concerned may defer the retirement under subsection (a) of an officer serving in a general or flag officer grade who is the Chief of Chaplains or Deputy Chief of Chaplains of that officer’s armed force. (2) A deferment of the retirement of an officer referred to in paragraph (1) may not extend beyond the first day of the month following the month in which the officer becomes 68 years of age.