Start by taking a deck of cards (if a few are missing it’s not a big deal) with the jokers at the bottom. Have a Volunteer From The Audience pick a card, memorize it, and put it back on top of the pile. Then hand the pile of cards to The Volunteer and let them cut the deck a few times. You can turn around or hide your eyes if you want to; it really doesn’t matter, but it looks a little more impressive.
Take the deck back, and tell The Volunteer that you’re going to need to put the jokers at the bottom of the pile. Quickly look at the cards face-up, and cut it where the jokers are so the jokers end up at the bottom of the pile. If possible, when you’re holding the cards face-up and looking for the jokers, start looking from the bottom of the pile and don’t show the card that was on top of the jokers [which ends up at the very top of the pile].
Turn the pile back face down. For this next part, all of the dealing and replacing is done with face-down cards. Ask The Volunteer how many weeks are in a year. (52) From the top of the pile deal a pile of 5 cards and a pile of 2 cards. Put the pile of 2 cards on top of the pile of 5 cards, and place them on top of the rest of the deck.
Ask The Volunteer how many months are in a year. (12) From the top of the deck deal a pile of 12 cards, and then put them back on top of the deck.
Ask The Volunteer how many days are in a week. (7) From the top of the deck deal a pile of 7 cards, and then put them back on top of the deck.
Finally, take the top card and put it somewhere in the deck (you can pretend to think about it and then reject it). Take the joker from the bottom of the deck, tap the top of the deck and say, “Bring up the chosen card!”, “A la peanut butter sandwiches!”, or something equally melodramatic, and then turn over the top card of the deck. It will be The Volunteer’s card!
I found this at Card Trick Central; the original author is unknown.