January 1, 1970 (at midnight) is Unix time 00:00:00 0.0. If the app is picking the time up from the SD card, and it's a counterfeit card, that could be the problem - a lot of counterfeiters aren't aware that resetting things on the card (like setting a 4GB card to say that it's a 128GB card) resets the date and time to 0. Use
SD Insight to check the card. (And if that's what's happening, it's probably because the apps were moved to the card, or the card is formatted as internal - neither of which is a good idea.)