Actually, I don't think you can reset it without using a cheat device. And I'm having trouble even finding a cheat code that can do that... This is odd. I've actually found a couple of sites with codes to change the clock in Ruby and Sapphire, but I can't find similar information for Emerald. It could be that no one's figured out a code yet, or it could also be that the programmers made the clock immune to manipulation without a player outright hacking the game. I'll try to look into this some more.