Each of your predictions is timestamped when first created with millisecond resolution. The timestamp is not editable and configured to Coordinated Universal Time (UTC).
All predictions are locked so as not to be edited or tampered with by anyone once created, ensuring that your friends (or enemies) believe that you made the prediction you say you did.
Use one of the built-in sharing mechanisms (Facebook, Twitter, email) or just copy the given link to share your prediction either before or after it comes true.