Section 110. The city council of a city may provide that the employees, including laborers, mechanics and all other classes of workmen employed by the city, shall be allowed one half holiday in each week without loss of pay during such portion of the year as the city council determines. The selectmen of a town, upon the recommendation in writing of the head of any town department, may provide that the employees of such department in the town, including laborers, mechanics and all other classes of workmen employed by the town, shall be allowed one half holiday in each week without loss of pay during such part of the year as the selectmen determine. This section shall not apply to any city or town which has accepted the provisions of section thirty-three A of chapter one hundred and forty-nine.