All deeds made and executed prior to January 1, 1940, by trustees conveying property sold under deeds of trust in which default was made in the debt secured and as to which irregularities in advertising such sales have occurred shall be held and the same are hereby declared valid in all respects, if otherwise valid according to law then in force, after the expiration of 15 years from the date on which such sale was made by such trustees.
Va. Code § 55.1-121