Tennessee Code Title 58. Military Affairs, Emergencies and Civil Defense § 58-1-212

(1) The date of rank is the date of federal recognition in the national guard; provided, that the officer has had no prior active federal or reserve component service in the same or higher grade;

(2) When an officer has had prior active or reserve component service in the same or higher grade, the officer's date of rank will precede the date of federal recognition by a period equal to the total length of such service (inactive service in either the army of the United States, reserve or national guard will not count);

(3) When the date of rank of two (2) or more officers is the same when computed under either subdivision (1) or (2), the senior will be determined by the length of active commissioned service in the national guard. Further determination will be made by total active commissioned service in all components, then by age.