I was wondering if there's any option to create sort of a time capsule in a Word document, i.e. not encrypted by password rather than a date. Let's say I send the document today but the receiving side can open the document only the next month on a specific date.
I know no feature like this built into any word processor. And, despite work on so-called time-capsule cryptography, we know no practical[*] way to implement one without relying on trusted hardware or trusted third party.
To achieve this, we can use the help of a trusted third party/server. It can generate and publish public keys for which it will publicly release the private keys at a set date. The sender enciphers the message with the public key selected per the desired release date. The receiver can't decipher until that date. To do so, s/he must get online, get the private key (now published) from the third party, then decipher.
[*] Problems with proposed time-capsule cryptography systems requiring no trusted external hardware/party are that their delay of release is too imprecise, and they would be prohibitively costly. They achieve timed release by requiring sequential iteration of a certain computation, assumed to require at least a certain time $T_0$. To obtain a delay $T$, the receiver is forced to perform $t=T/T_0$ operations, at full rate, during the whole timed release. But $T_0$ varies a lot with the technology, and the fasted high-speed logic is prohibitively expensive. That used to be GaAs, now perhaps InP, or is it unobtainium-on-diaphire immersed is liquid nitronium.