This is really one of those questions where you want X, you started down the path of answering the question but got stuck, and now are asking how to get unstuck

This is really one of those questions where you want X, you started down the path of answering the question but got stuck, and now are asking how to get unstuck when you should be asking for X. He's asking "how to decrypt only after a certain date" when in reality he should be asking "how to make information available after a certain date".