This 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 with 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 looking at you, set the time on YOUR watch. Your other hand is moving their stem so THEIR time 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, and pick a higher number. It gets them everytime... just remember to give a great patter when doing this trick. TIPS: I recommend trying to do this on nervous or shy people so they don't know what you're doing. The key to this trick is misdirection , but it's very easy to get caught.