This charter shall take effect on the date or at the times stated in the amending ordinance or, if an election is held thereon, then it shall take effect at the end of thirty days from the date of such approving election. The first election under this charter shall be held on November 3, 1970, at which time a mayor and six aldermen, as herein provided for, shall be elected. The mayor shall be elected to a four-year term. The three aldermanic candidates in each ward receiving the largest number of votes shall be declared elected. But to assure the council of the continuity of staggered terms (1) the elected alderman in each ward receiving the largest number of votes shall be elected to a term of four years, (2) the elected alderman in each ward receiving the smallest number of votes shall be elected to a term of two years, and (3) as between the two remaining elected aldermen (one from each ward, the one receiving the larger number of votes shall be elected to a term of four years and the one receiving the smaller number of votes shall be elected to a term of two years. Thereafter, all terms shall be four years as herein provided. Terms of the present mayor and aldermen shall be, and they are hereby, lengthened or shortened, as the case may be, and end when the officials so elected assume office at the first council meeting in January, 1971.