Section 272(6)(a) in The Naval Ceremonial, Conditions Of Service And Miscellaneous Regulations, 1964
(a)Ex-Servicemen re-entering after having been absent from the service for more than 3 years (more than 5 years in the case of Reservists) shall not be permitted to count their previous service and shall be treated as new entrants. Sailors re-entering within 3 years (5 years in the case of Reservists) will count their previous qualifying service for all purposes.