10 ILCS 5/6-30
If any city, village or incorporated town adopts and becomes entitled to the benefits of this Article 6 and Articles 14 and 18 of this Act, after the date for the first registration hereunder, registration therein shall be governed by the law applicable thereto at the time of the adoption of said Articles until a complete first registration can be had. Such first registration shall be in the manner provided in this Article and shall precede the primary held for the nomination of candidates for the next succeeding congressional election, and the periods provided for each step in such registration shall be the same as are provided by this Article 6 with respect to cities, villages and incorporated towns subject to this Article at the time when it takes effect. A period for registration at the office of the board of election commissioners prior to such election shall be allowed equal to that provided by this Article, for the period intervening between the first Tuesday in August, 1936 and the first Tuesday after the first Monday in November, 1936.
10 ILCS 5/6-30