Do you need one of the events to get the regi trio on pokemon platinum?

Well the way I obtained the Regi-Trio, I needed an event. A while back, they had an event for Pearl and Diamond which gave you a Regigigas. Lv. 100 and amazing! You then transfer him to Platinum, and the old abandoned caves in Iron Island, Mt. Coronet, and route 228 become the resting places for the Regis. Iron Island for Registeel, Mt. Coronet for Regice, and route 228 for Regirock. Look up the Action Replay code for the Regigigas.