For the less cryptographically inclined, or those predicting the failure of computing technology, there is always the old school method: write your prediction on a peace of paper, literally seal it in an envelope, and mail it to yourself. The postal marking they put over the stamp includes the date.
For the less cryptographically inclined, or those predicting the failure of computing technology, there is always the old school method: write your prediction on a peace of paper, literally seal it in an envelope, and mail it to yourself. The postal marking they put over the stamp includes the date.