Where two or more adjacent lots, one or more of which is nonconforming, are owned by the same owner, and the ownership of the lots is concurrent, such lots shall be deemed to be merged into a single conforming or more closely conforming lot. For the purpose of this chapter, the merger of nonconforming lots shall occur upon the date said lots became nonconforming or upon the date when adjacent property is purchased by the same owner, whichever date shall first occur.