No county sheriff shall qualify for membership in the Police and Firemen's Retirement System of New Jersey pursuant to this amendatory and supplementary act if he has reached the age of 37 years on the date of his application for membership. In calculating his age for purposes of eligibility for membership, a person may subtract the time spent in active service in any branch of the United States military service.
N.J.S. § 43:16A-3.6