Okla. Admin. Code § 715:10-5-10
An active contributing member of TRS may purchase credit for active duty service in the Armed Forces of the United States of America. The member must have received an honorable discharge from the Armed Services to qualify for military service credit. Active duty is defined as that time a member served in the Armed Forces of the United States of America from the date inducted to the date of separation. (Time spent between enlistment and induction, or other time spent as a civilian between military service periods, will not be counted as military service.) Credit for military service shall not exceed the number of years obtained when the total months of service are applied to calendar years (January 1 to December 31 periods). Therefore, thirty-six (36) months of military service cannot count for more than three (3) years of TRS membership; forty-eight (48) months cannot count for more than four (4) years; etc.
Okla. Admin. Code § 715:10-5-10