Out of the link (Slow305) posted right above me...
California
The age of consent is 18, with a misdemeanor if the minor has 3 or fewer years of difference with the major, and potentially a felony if the major is more than 3 years older. It is worth emphasizing that unlike most other states, the close-in-age rule in California (3 years) do not provide an exception nor provide any defense; it merely lowers the crime to a misdemeanor. Under this law, two minors of the same age could both be prosecuted. Penalties increase if the minor is under 16 and the major is above 21 or if the minor is more than 3 years younger.