California

§ 261. 5(b)-(d)
Anyone who engages in an act of unlawful sexual intercourse with a person under age 18 and the actor is not more than three years older or three years younger, is guilty of a misdemeanor

Anyone who engages in an act of unlawful sexual intercourse with a person under age 18 who is more than three years younger than the actor is guilty of either a misdemeanor or a felony

Any person 21 years of age or older who engages in an act of unlawful sexual intercourse with a minor who is under 16 years of age is guilty of either a misdemeanor or a felony
Up to one year in county jail

Up to one year in county jail or by imprisonment in the state prison (period unspecified)

Up to one year in a county jail or by imprisonment in the state prison for two, three, or four