I created a free and open source Bitcoin Time Capsule called BTCapsule. It uses the timestamp from the Bitcoin blockchain, and allows you to enter your private keys and check them without exposure to the internet

BTCapsule is a Bitcoin Time Capsule for your private keys. You simply copy the program to a USB flash drive, run it, enter a year and your private keys, and it’s saved in an encrypted file.

You can then give the flash drive to a loved one, tell them to install Bitcoin Core, and when the year comes to pass, they will have access to your private keys. There is no need to remember a password or PIN number. The year you choose is the password.

BTCapsule is open source and free to download. If you find value in BTCapsule, please consider donating some sats on my website. I hope you like it!

Source code:

https://github.com/BTCapsule/BTCapsule

BTCapsule converted to C and compiled to machine code can be downloaded here:

https://btcapsule.com/