In computing length of creditable service under the Nebraska State Patrol Retirement Act, such service shall include the years of service with the Nebraska State Patrol, permanent force, as established by the law creating the Nebraska State Patrol computed to the nearest one-twelfth year and shall only include such years during which the person was a contributing member of the Nebraska State Patrol Retirement System. Length of creditable service shall also include credit for time served in the armed forces pursuant to section 81-2034. For subsection (2) of section 81-2031 only, service shall also include credit for vesting pursuant to sections 60-1304, 81-2016, and 81-2031.02.