I bring to your attention the SHA256 HASH of this secret coin - in 12-24 months I will publicly announce this coin and you will compare whether it is true or false. If this turns out to be true, don't be too upset, next time you will definitely be lucky - 83d2e1edf511c74e6cd922258f7cfd5f034750c768021450a613982580a57bce
Good idea actually, this is what blockchain/crypto is for. And if you wanted to prove you made the prediction today, just attach that hash to a BTC TXid and it's etched-in.