BYTE -- By default, your Nintendo 3DS is set to midnight, Jan. 1, 2011. If you clear your system memory or replace the battery, the setting will revert to that.
Because the 3DS keeps an activity log and games like Animal Crossing: Wild World rely heavily on real-world date and time, you want to make sure those settings are correct. Here's how.
I'll start with resetting the date. From your 3DS home menu, hit the left arrow to page left. You will see a small wrench icon. Tap on that to go into System Settings.
Next tap on Other Settings in the bottom-right corner.
Now choose Date & Time.
From the submenu you see -- Today's Date and Current Time -- fix the date. Touch Today's Date.
Enter the date by using the up and down arrow keys and hit OK.
You'll receive a warning screen informing you that changing the date and time may cause data in some applications to be displayed incorrectly. Ignore that and hit OK again.
Now fix the time. From the Today's Date and Current Time menu, select Current Time
Set the 3DS to the current time by adjusting with the up and down arrows.
Keep in mind that the machine is using a 24-hour clock. Hit OK.
Hit the back button in the bottom-left corner to exit the Date & Time settings. Close the menu and you're done.
This comes in exceptionally handy when you swap out your Nintendo 3DS battery.