"Time is of the essence" is a term in English and United States contract law expressing "the need for timely completion", i.e. indicating that one or more parties to the agreement must perform by the time to which the parties have agreed if a delay will cause material harm. However, in the case of Foundation Development Corp. v. Loehmann's Inc. 788 P.2d 1189 (Arizona 1990), in which the lease included a Time is of the essence clause, the court ruled that a minor delay did not cause material harm and thus no breach of contract occurred.
Compare this to an "express clause", where a specific contract term must be performed to avoid breach, such as in the court decision in Dove v. Rose Acre Farms, Inc. 434 N.E.2d 931 (Ct. App. Ind. 1982).
Contrast this with reasonable time, where a delay in performing may be justified if it is reasonably required, based upon subjective circumstances such as unexpected weather.