Hacking Boot.elf instead of Boot.dol

[JoostinOnline]

Can't you just turn off your wifi?

Turning off wifi won't delete the current level. It's not too long before the 24 hours are up though, so it shouldn't be a problem. The OP might still consider turning off wifi just in case he accidentally clicks the online part. It won't hurt anything.

I don't understand how this works. Does he download a stage via wifi and it stays installed until a certain date? If yes, wifi off, set your date to next year, done. And if the stage is installed, does it become part of the savegame, or is it listed(and deletable) as extra savegame in the menu?

The stage downloads when you connect. They are user submitted stages. It has been awhile since I have used SSBB, but I believe it stays until 24 hours later. I suppose it makes sense that setting the date forward would fix it. I do remember that it becomes part of your save file, and can't be moved to your SD card (which would let you delete it).