N.Y. Est. Powers & Trusts Law § 10-8.4

§ 10-8.4 Rule against accumulations; law determining validity in\n exercise of a power of appointment\n When a direction for the accumulation of income is contained in an\ninstrument exercising a power, heretofore or hereafter created, the\nvalidity of such direction is determined by the law in effect when the\npower is exercised, and not by the law in effect when the power was\ncreated.\n