New York Consolidated Laws, Civil Practice Law and Rules - CVP § 217. Proceeding against body or officer; actions complaining about conduct that would constitute a union's breach of its duty of fair representation; four months

2. (a) Any action or proceeding against an employee organization subject to article fourteen of the civil service law or article twenty of the labor law which complains that such employee organization has breached its duty of fair representation regarding someone to whom such employee organization has a duty shall be commenced within four months of the date the employee or former employee knew or should have known that the breach has occurred, or within four months of the date the employee or former employee suffers actual harm, whichever is later.

(b) Any action or proceeding by an employee or former employee against an employer subject to article fourteen of the civil service law or article twenty of the labor law, an essential element of which is that an employee organization breached its duty of fair representation to the person making the complaint, shall be commenced within four months of the date the employee or former employee knew or should have known that the breach has occurred, or within four months of the date the employee or former employee suffers actual harm, whichever is later.