The effective date of ordinances shall be prescribed therein, but the effective date shall not be earlier than fifteen (15) days after the enactment nor before publication thereof, except that ordinances immediately necessary for the preservation of the public peace, health or safety may be given earlier effect by the affirmative vote of not less than three Councilpersons if three or four Councilpersons are present at the meeting, and by the affirmative vote of not less than four (4) Councilpersons if five (5) Councilpersons are present at the meeting. In case an ordinance is given effect earlier than fifteen (15) days after its enactment, all requirements for publication may be met by posting copies thereof in conspicuous locations in three (3) public places in the City; and the Clerk shall, immediately after such posting, enter in the Ordinance Book under the record of the ordinance a certificate under his/her hand stating the time and place of such publication by posting, which certificate shall be prima facie evidence of the due publication and posting of the ordinance.