Settings for new user won't save

I was given an old ds by a friend who had lost the cable. I find my old one in storage, and get it charging. It boots up fine, the bottom screen is a little scratched, but it's still in good condition. But for some reason, it accepts the nickname, color, and birthdate, but the date and time stay all 0's after I hit accept. Then, when it says it needs to restart so the new settings take effect, the new settings haven't taken effect. Help?