California Code, Government Code - GOV § 34900

At any general municipal election, or at a special election held for that purpose, the city council may submit to the electors the question of whether electors shall thereafter elect a mayor and four city council members, and whether the mayor shall serve a two-year or four-year term.  In cities presently having elected mayors, the city council may also submit to the electors the question of whether the mayor shall thereafter serve a two-year or a four-year term.