Before any change, amendment, supplement or reclassification becomes effective, a public hearing shall be held. Notice of same shall be given by one publication in a newspaper of general circulation in the City at least fifteen days before the date of such hearing. The notice shall state the place or places and time or times at which the proposed amendment to the Zoning Ordinance, including text and/or Map, may be examined. The Planning Commission may be directed to conduct all necessary public hearings incident to any proposed amendment, supplement or change in regulations or boundaries of districts.