Section 58A. Notwithstanding the provisions of any general or special law to the contrary, in any city, town or district that accepts this section, no person shall be eligible to have his name certified for original appointment to the position of firefighter or police officer if such person has reached his thirty-second birthday on the date of the entrance examination. Any veteran shall be allowed to exceed the maximum age provision of this section by the number of years served on active military duty, but in no case shall said candidate for appointment be credited more than four years of active military duty.