Central Standard Time shall be the official time within the city for the transaction of all city business; except that from 2:00 a.m. on the first Sunday in April of each year, official time for the city shall be advanced one hour and at 2:00 a.m. on the last Sunday in October in each year the official time shall by the retarding of one hour be returned to Central Standard Time. All legal or official proceedings of the City Council and all official business of the city shall be regulated as to time in accordance with the provisions of this subchapter; and when by ordinance resolution for action of any municipal officer for any municipal body an act must be performed at or within a prescribed time, it shall be performed according to the official time as herein prescribed. When the words “Daylight Saving” or “Daylight Saving Time” are used in any official document or contract it shall be understood to have reference to the time herein fixed for the period from the last Sunday in April to the last Sunday in October.