"Biennial" is a confusing word. The Nevada legislature meets biennially, i.e., every other year while the California legislative session is biennial, i.e., lasting two years. "Biennial" should not be confused with "biannual" which normally means twice a year.
The California legislature meets annually but the legislative session is biennial. Last Monday, for example, the California legislature convened for the 2017-2018 legislative session. Cal. Const. Art. IV, § 3(a). The last day to introduce bills will be February 17, 2017. Joint Rules of the Senate and the Assembly (J.R.) 61(a)(1) & J.R. 54(a). No bill, other than the Budget Bill, may be heard or acted upon by committee or either house until the bill has been in print for 30 days. J.R. 55. Friday, September 15, 2017 will be the last day for either house to pass bills. J.R. 61(a)(15). The Governor will have until October 15, 2017 to sign or veto bills passed by the legislature on or before September 15 and in his possession after September 15, 2017. Cal. Const. Art. IV, Sec. 10(b)(1). The legislature will reconvene for the second year of the biennium on January 3, 2018. J.R. 51(a)(4).
The Nevada legislature is one of only four state legislatures that meets biennially. The other three states are Montana, North Dakota and Texas. Nevada's regular legislative sessions begin on the first Monday in February in odd numbered years and are limited in length to 120 calendar days by the Nevada Constitution. See “Does Anybody Really Know What Time It Is?”