In the event that the date for the holding of any state or municipal election, other than the general election held on the first Tuesday next after the first Monday in November in even numbered years, falls upon the day of a religious holiday on which the doctrines of a faith would prohibit its followers from voting, the election shall be held upon the next business day other than Saturday then following; provided, that nothing contained in this section shall be deemed to invalidate any election once it has been held.