—Order unanimously modified on the law and as modified affirmed without costs in accordance with the following Memorandum: Plaintiff commenced this divorce action in December 1994. Supreme Court did not err in determining that the 1994 contribution of defendant to his Keogh plan was subject to equitable distribution. Although the contribution was not made until April 1995, after the commencement of the divorce action, the court properly determined that it came from 1994 earnings.

The parties entered into a written property settlement agreement and a custody agreement that were incorporated but not merged into the judgment of divorce. The court properly determined that, pursuant to the property settlement agreement, plaintiff is entitled to one half of defendant’s Keogh plan and that defendant is entitled to one half of plaintiffs 40 IK, IRA and pension plans. The court erred, however, in directing that the parties are entitled to one half of the average appreciation of those plans from 1994 to the present. The property settlement agreement is an independent contract that is subject to the principles of contract interpretation (see, Rainbow v Swisher, 72 NY2d 106, 109; Keith v Keith, 241 AD2d[*808] 820, 822; De Gaust v De Gaust, 237 AD2d 862), and it provided that the date of valuation of the retirement plans was the date of the commencement of the action. Because the value of defendant’s retirement plan exceeds that of plaintiffs, defendant must pay plaintiff the difference. Considering the delay in the final resolution of this matter, we exercise our discretion to award plaintiff interest on that amount at the statutory rate (see, CPLR 5004) from the date of commencement of the action (see, Selinger v Selinger, 232 AD2d 471, 473, lv dismissed 89 NY2d 981, 90 NY2d 842, rearg denied 90 NY2d 937; Trivedi v Trivedi, 222 AD2d 499). We thus modify the order accordingly. (Appeal from Order of Supreme Court, Erie County, O’Donnell, J. — Matrimonial.) Present — Hayes, J. P., Hurlbutt, Balio and Lawton, JJ.