Please don’t set your iPhone to 1970
/You may have heard of a rumour that if you set your iPhone’s date to January 1st 1970, you will receive a retro Apple theme on your iPhone. However, this will actually cause your iPhone to stop working, and at the moment it cannot be fixed! Apple still can’t figure out what the problem is, and you will have to have your iPhone replaced. Apparently this happens as January 1st 1970 is the first day of Unix time. Unix time is counted in seconds, making January 1st 1970 appear as 00:00:00 in Unix time.
If you're curious about seeing the effects of changing the date of your iPhone to January first 1970, then you can see this online with plenty of videos on the internet showing these effects. The good thing is that you can’t do this accidentally, changing the date has to be done manually.