Anytime when the Time Capsule is up and running.
OK. Well first, you must have Pokemon Gold or Silver version, two Game Boys, and a copy of Pokemon Red or Blue. You also have to have a link cable. To do this, play through the Blue and/or Red game until you make it to the Pokemon that you want on Gold or Silver. Simple. Just catch the Pokemon, and head to the Pokemon Center in both games. Be sure to link up the two Game Boys with the link cable. Then, for Gold/Silver, go to the Time Capsule, and on Blue/Red go to the Cable Club. Trade the good Pokemon with some Pokemon that you don't really care about. Do this a lot, and you'll not only have rare, legendary Pokemon, but you could also get a pretty good shot at winning the Lottery. Happy Gaming!!!