HNC §7121: (a) No ordinance shall become effective until 30 days from and after the date of its passage, except the following: (1) An ordinance calling or otherwise relating to an election.

(a) No ordinance shall become effective until 30 days from and after the date of its passage, except the following: (1) An ordinance calling or otherwise relating to an election. (2) An ordinance for the immediate preservation of the public peace, health, or safety, that contains a declaration of, and the facts constituting, its urgency, and is passed by a four-fifths vote of the board. (b) Prior to the effective date thereof ordinances shall be subject to referendum in the same manner and with the same effect as ordinances of counties under Article 2 (commencing with Section 9140) of Chapter 2 of Division 9 of the Elections Code and terms used therein shall have the meanings set forth in Section 7120.