I woke up and then spent Sunday afternoon playing Miitopia on the Nintendo Switch 2 for three hours, then in the evening I watched some episodes of My Little Pony Friendship is Magic. So I really enjoyed this Sunday!
The time and day changes are caused by the battery being incorrectly positioned in the 3DS, which is why the day, time, and year are reset every now and then. However, the battery only lasted 30 minutes at most unless I kept the 3DS charged.