of the essence.(Of a contractual requirement) so important that if the requirement is not met, the promisor will be held to have breached the contract and a rescission by the promisee will be justified <time is of the essence>. [Cases: Contracts 211; Vendor and Purchaser 78.C.J.S. Contracts § 583; Vendor and Purchaser § 140.]

[Blacks Law 8th]