10 U.S.C. § 1405

(a) In General .— For the purposes of the computation of the years of service of a member of the armed forces under a provision of this title providing for such computation to be made under this section, the years of service of the member are computed by adding— (1) his years of active service; (2) the years of service, not included in clause (1), with which he was entitled to be credited on May 31, 1958 , in computing his basic pay; and (3) the years of service, not included in clause (1) or (2), with which he would be entitled to be credited under section 12733 of this title if he were entitled to retired pay under section 12731 of this title . (b) Fractional Years of Service .— In determining a member’s years of service under subsection (a)— (1) each full month of service that is in addition to the number of full years of service creditable to the member shall be credited as 1 ⁄ 12 of a year; and (2) any remaining fractional part of a month shall be disregarded. (c) Exclusion of Time Required To Be Made Up or Excluded .— (1) Time required to be made up by an enlisted member of the Army, Air Force, or Space Force under section 972(a) of this title , or required to be made up by an enlisted member of the Navy, Marine Corps, or Coast Guard under that section with respect to a period of time after October 5, 1994 , may not be counted in determining years of service under subsection (a). (2) Section 972(b) of this title excludes from computation of an officer’s years of service for purposes of this section any time identified with respect to that officer under that section.