How to fix the date?

You have to go to your DS main settings and change the date there thats the only way I know

You go to options on the list of things for example where it says brain age challenge ect then when you have clicked on options you go to date/time then change it to what you want
I hope this helps

on your actual ds console there is alittle picture downnthe bottom in thye middle of a ds then once you r on there there r for coloured things u go to the blue one then once u are on there you go on the first top one then u change date and time thts the only way you can do it then once you done tht on your ds it will be ok on yor game
i hope this helps
good luck

on your ds you go to the ds icon that is down the bottom then there is 4 colours tht come up you go on the blue one then u go to the top one then u change the date and time
hope this helps
goodluck

The procedure to fix it varies depending on what sort of DS you have. This is what you do with a DS Original or DS Lite:
If you're on automatic mode or you have an R4 or other flashcart then remove the cartridge. Then turn your DS on so that the menu comes up. Click the DS icon in the bottom.
Click the blue calendar icon, then click the calendar icon to fix the date, or the clock icon to fix the time.