New York Consolidated Laws, Family Court Act - FCT § 714. Determination of age

(a) In determining the jurisdiction of the court under section seven hundred thirteen the age of the respondent at the time the need for supervision allegedly arose is controlling.

(b) If the respondent is within the jurisdiction of the court, but the proceedings were initiated after the respondent's eighteenth birthday, the family court shall dismiss a petition to determine whether a person is in need of supervision.