This is overcomplicated and unnecessary for the case described by Poker Player. He wants to make the message public after a certain event, so there is no need to encrypt the message. It is sufficient to sign or hash a message and publish its signature/hash in advance, so that anyone can verify, and you don't depend on one or two forum members to confirm the authenticity of your message.

Poker Player, if you want to add a timestamp to your message, I suggest that you incorporate the block number and the nonce from the last mined block into the message. When you publish the signature/hash of the message, you also publish the block number and nonce that will be in the message. That way, you will have another provable way of confirming when the message was created.