In providing for the convening of a constitutional convention to amend or revise the constitution of the state the general assembly shall, upon roll call, by a yea vote of at least two-thirds of the total membership of each house, prescribe by law the manner of selection of the membership of such convention, the date of convening of such convention, which shall be not later than one year from the date of the roll call vote under Section 1 of this article or one year from the date of the election under Section 2 of this article, as the case may be, and the date for final adjournment of such convention.