What is a day in a contract?

In Elements (Europe) Ltd v FK Building Ltd, a provision in a contract provided that an application had to be received "not later than 4 days prior to [in this case, 25th October]". Was an application sent by email on 21 October at 22.07 sent on time? The judge held that it was.

Reference to a "day" in a contract does not mean four clear days: "Thus, in my judgment, construing the words according to their natural language and usage, if it is necessary to do X not later than 4 'clear' days prior to date A, X must be done, at the latest, on the fifth day prior to date A. By contrast, it if X is merely to be done '4 days' prior to date A, X may be done on the fourth day prior to date A". Furthermore, any time up until midnight on 21 October was all right: "because the law does not count in fractions of a day".