Русско-англо-русский юридический словарь

Reasonable time refers to the amount of time that is fairly required to do whatever is required to be done, conveniently under the permitted circumstances.

In contracts, reasonable time refers to the time needed to do what a contract requires to be done, based on subjective circumstances. If the parties entering the contract do not fix a time for performance, the law will infer a reasonable time within which it should be done.

Under commercial law, Uniform Commercial Code UCC 2-206(2) requires that acceptance of an offer be made within a "reasonable time" if no time is specified. (definitions.uslegal.com)

Reasonable Time. In the absence of an express or fixed time established by the parties to an agreement or contract (especially one that falls under the purview of the Uniform Commercial Code [UCC]), any time which is not manifestly unreasonable under the circumstances. For example, if a contract does not fix a specific time for performance, the law will infer (and impose) a reasonable time for such performance. This is defined as that amount of time which is fairly necessary, conveniently, to do what the contract requires to be done, as soon as circumstances permit. The term "reasonable time" has other (related) applications: UCC 2-206(2) requires that acceptance of an offer be made within a "reasonable time" if no time is specified. (West's Encyclopedia of American Law, edition 2)