So wear that Victorian daydress or air-pirate costume to the mall or the grocery store–pretend to be amazed, or simply go about your business as if there’s nothing strange about it.
Or, walk up to random people, ask them the date, freeze, then sigh with relief and go, “great, there’s still time,” and run off.
Hand someone a random trinket and tell them that if they value humanity they’ll bury it in their backyard–today.
Wear a mash of clothing from the past couple of decades and pretend to not quite fit it or be able to quite use “modern” technology.
You could also simply choose to offer sanctuary to other time travelers by hanging the universal time traveler’s symbol in your window.
Whatever you do today…have fun! And if you missed it…just pretend to travel back in time so you don’t miss it.