Instructions
Change the Wii's date if you do not want to wait for New Year's Day. To change the clock, go to the Wii System Settings menu.
Select "Calendar." Click the arrows to set month to "1" and the day to "1." You do not need to change the year. Select "Confirm."
Load your game. Go to the Town Hall and speak with Tortimer. He hands you the New Year's shirt as a free gift.