It's a practice hack/mod

1. It requires homebrew
2. They have the time set back on their switch.

It’s just a part of the mod it does that for some reason

You can use practice mod on emulator but unless you have a really nice pc, it won't run well and there's no point in using it to practice. The 1970 date is part of the mod. If you want to do it on your switch you will have to mod it.

Tyron has a video on how to do it I believe(it might be outdated tho, idk)