Section 12A. A charter submitted to the voters in accordance with the provisions of this chapter which has failed of approval at a city or town election, but which has received the affirmative votes of not less than thirty-five per cent of those voting on the question, shall be considered an optional charter for such city or town. Upon the petition of ten per cent of the registered voters of such city or town, said optional charter shall be once resubmitted to the voters at a regular city or town election held no later than the second year following the original submission of such charter to the voters. The city council in a city, the town council in a town having a town council, and in every other town the board of selectmen, shall cause any changes to be made in dates in the charter as originally submitted to the voters which are necessary to ensure the orderly implementation of the optional charter.