The date will appear on the very first page of the trust and it will also be the date that you sign on the execution page where your signatures and the notary appear.
This date will remain the date of the trust for as long as the trust exists. You can change it, you can restate it, you can amend it, you can change every provision in that document, but because the original date stays the same, all of your funding remains the same and you don't have to go back and redo any funding just because you change your mind about who gets what when you die, or who's going to be your successor trustee, or who is going to determine your incapacity, or if you want to add property to the trust.
If you're actually revoking a trust and starting fresh, it will have a new date and a completely new funding requirement.