At all city elections the polls shall open at 7:00 a.m. and close at 7:00 p.m., unless different hours are set and publicly announced by the county election officer. In the event that different hours are so set, the polls shall be open at least twelve (12) continuous hours commencing not earlier than 6:00 a.m. and ending not later than 8:00 p.m. The secretary of state shall adopt rules and regulations specifying the time and manner of setting and announcing any change of hours under authority of this section.