The council of the city shall provide for the manner in which the regulations and restrictions and the boundaries of the districts shall be determined, established, and enforced, and from time to time amended, supplemented, or changed. However, the regulation, restriction, or boundary shall not become effective until after a public hearing at which parties in interest and citizens shall have an opportunity to be heard. The notice of the time and place of the hearing shall be published as provided in section 362.3, except that at least seven days’ notice must be given and in no case shall the public hearing be held earlier than the next regularly scheduled city council meeting following the published notice.