Effect: David Blaine did this watch trick on his second national TV special. A watch is borrowed, the magician does not carry anything! After showing the watch to those nearby who notice the current time, you place the watch face down in the spectator's hand. His hand is closed over the watch. The magician does not touch the watch again. The magician then asks the spectator to name a number and then to concentrate on that number and the watch. He opens his hand, turns over the watch and sees that the hands of the watch have moved that many minutes ! This watch trick does not require any gimmicks.
Props: Someone wearing an analogue watch ( a watch with an long stem that's easy to manipulate quickly. i.e.: SEIKO watches )
Preparation: You need to wear a watch of your own, set at the wrong time.
Method: Ask your victim for his watch with an excuse like, "I think my time is wrong can I see yours for a second?"
Borrow the watch for a minute and examine it look at it, state what time it has, and say, "Is this the right time, I need to know."
Now glance at the time on YOUR watch, and draw attention to it by setting its time. While they are looking at you setting the time on your watch, your other hand is moving the stem on their watch so that the time on THEIR watch is moved forward 25 minutes. Now have them sandwich their watch between their hands and ask them to pick a number from 10 through 30. Most people will pick 25. If they pick 20, they won't notice it's off by five minutes when you reveal that the hands of their watch have moved forward in time.... If they pick something below that number, tell them to make it harder for you, and pick a higher number. It gets them everytime... just remember to come up with some great patter when doing this trick.
I recommend trying to do this on nervous or shy people as they tend to be more easy to distract and are less suspicious. The key to this watch trick is misdirection, but it's very easy to get caught.