Decryption possible only within a period of time Time-locked encryption and time-released encryption seem to be security systems focused on making sure that the decryption of certain message cannot take place before a certain time has passed.

However, I was wondering if there's in cryptography something aiming at the opposite of the above, so I would like to make the decryption possible ONLY during a certain period of time but NOT after that time has passed.

Would it be possible? If so, which mechanism do you know achieving this?
This is possible, but only if you introduce one or more parties in addition to the sender and receiver. Also, the receiver must be online when decrypting.

Typically, the security requirements would be that (a) if the recipient tries to decrypt inside the time window, he should be able to decrypt, even if the sender is not cooperating; (b) if the recipient did not decrypt the message inside the time window, he should not be able to learn anything about the contents of the ciphertext; and (c) any additional parties should not learn anything about the ciphertext.

From such requirements, it should be fairly straight-forward to come up with reasonable schemes. Some variant of threshold decryption should do the trick.