Русско-англо-русский юридический словарь

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)

The English law, which in this respect, has been adopted by us, frequently requires things to be done within a reasonable time [...] A bill of exchange, for example, must be presented within a reasonable time Chitty, Bills, 197-202. An abandonment must be made within a reasonable time after advice received of the loss. (A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier.)