Choose one of the training modes at the menu. Get your stamp for the day then turn off the Nintendo DS. Turn on the Nintendo DS and change the date to the next day. Turn off the Nintendo DS so that your changes can be saved. Keep repeating this until you unlock all the training modes. When you have unlocked them all, turn off the Nintendo DS and change the date back to the correct value. This may effect your graph but you will still have all of the training modes unlocked.