Mass. Gen. Laws ch. 32 § 58A
A veteran eligible to retirement under section fifty-six, fifty-seven or fifty-eight, who was employed in the service of the commonwealth, or any county, city, town or district or any housing authority or any redevelopment authority thereof, prior to his entry into wartime service as defined in section one of chapter thirty-one, and upon whose discharge or release therefrom was reinstated or reemployed within two years in his former position or in a similar position or when employed in any governmental unit in a position which is subject to the provisions of sections one to twenty-eight, inclusive, shall have credited to him as creditable service the period of his wartime service until the date of his discharge or release from such service, which shall include credit for any actual service in the armed forces between January first, nineteen hundred and forty and the termination of the Selective Service Act of 1948; provided, however, that such service shall not be construed to include service for more than four years unless such further period of service in excess of four years was involuntary service required by the government of the United States or unless such service in excess of four years was rendered prior to July first, nineteen hundred and sixty-four and such veteran was reinstated or reemployed on or before June thirtieth, nineteen hundred and sixty-six.
Any such veteran who was employed in the service of the commonwealth or any county, city, town or district thereof and who was a member of a reserve component of the armed forces which was called to active duty by order of the president of the United States shall have credited to him as creditable service the period of such active duty performed between October first, nineteen hundred and sixty-one and the termination of the Selective Service Act of 1948, provided that upon the termination of such active duty or his discharge or release therefrom he was reinstated or reemployed within two years in his former position or a similar position.
Mass. Gen. Laws ch. 32, § 58A