http://www.ageofconsent.com/california.htm
For the purposes of this section, a "minor" is a person
under the age of 18 years and an "adult" is a person
who is at least 18 years of age.
(b) Any person who engages in an act of unlawful sexual
intercourse with a minor who is not more than three years
older or three years younger than the perpetrator, is
guilty of a misdemeanor