When, by the provisions of this charter or the laws of the State, notice of any matter or proceedings is required to be published or posted, an affidavit of the publication or posting of the same made by the printer of the newspaper in which the same was inserted or by some person in his employ knowing the facts, if such notice was required to be by publication, or by the person posting the same when required to be by posting, shall be prima facie evidence of the facts therein contained. Such affidavit of publication or posting shall be filed with the city clerk within six months from the date of the last publication thereof or the posting of the same.