The council shall hold a regular meeting at least once each month in the city at a time and at a place which it designates. It may adopt rules for the government of its members and proceedings. Upon the motion of the Mayor, or at the request, of three members of the council shall, by giving notice thereof to all members of the council then in the city, the mayor may call a special meeting of the council for a time not earlier than three nor later than forty-eight hours after the notice is given. Special meetings of the council may also be held at any time by the common consent of all the members of the council.