Open the back, there should be a window there that the LEDs shine through. Covering that up with some tape is the only thing I can think of to get rid of the date stamp. Not sure if that would cause any problems with the film or not though... (Assuming that it's a SLR, if it's not I don't think there's much you can do.)
Hmm... Yeah, I'm sure there's an option to turn it off (I don't know why I didn't think of that earlier...).