Neb. Rev. Stat. § 19-3701: Neb. Rev. Stat. § 19-3701

All ordinances for the government of any city of the first class, city of the second class, or village, adopted by the voters of such city or village after submission to them by either initiative or referendum petition, shall become immediately effective thereafter. No ordinance for the government of any such city or village except as provided in sections 16-405 and 17-613 , which has been adopted by such city or village without submission to the voters of such city or village, shall go into effect until fifteen days after the passage of such ordinance.