The Massachusetts obsolete mortgage statute, G.L. c. 260, § 33, provides, in relevant part, that "power of sale in any mortgage of real estate shall not be exercised . . . nor proceeding begun for foreclosure of any such mortgage after the expiration of . . . 5 years from the expiration of the term or from the maturity date." The purpose of the statute is to create a date certain by which an old mortgage is deemed discharged as a matter of law in order to provide certainty for title examiners and thereby remove impediments to the purchase and sale of real estate subject to mortgages for which a discharge was never filed in the applicable Registry of Deeds.