Any regulation or provision of this title may be changed and amended from time to time by the council. Such changes or amendments shall not become effective until after study and report by the commission and after a public hearing has been held by the council, public notice of which shall be given in such newspaper of general circulation not less than four (4) days but not more than twenty (20) days prior to the date set for said hearing. Approval of a change or amendment by council shall be by ordinance. (2008 Code § 28-8)