Not expected, anticipated or foreseen.

(rare) Someone or something unexpected.

plural of unexpected

Not to be expected; unusual or unpredictable.

(obsolete) Absence of expectation; want of foresight.

Not expectant.

Not expecting.

(rare) The condition of being unexpectant

Do not be surprised by unusual events. Anything might happen.

A paradox about a person's expectations about the timing of a future event which they are told will occur at an unexpected time. It is based on the idea that a prisoner, told that he will be hanged on a day unknown to him, concludes that "I cannot be hanged on Friday because if I haven't been hanged by the end of Thursday then it would no longer be a surprise", and so on backwards through the week.