When, prior to February 13, 1967, in any city with a population of 100,000 or less, a majority of the legal voters voting on the proposition of whether the city election law shall be rejected, as provided in Section 6-18, have voted in favor of the rejection of the city election law and the election is in other respects in conformity with law, the publication of the election notice is declared to be legal and valid and the election is validated, notwithstanding that the publication was only 12 days prior to the election by publication in one or more newspapers of general circulation published within the city.