Don’t worry; your computer isn’t being transported back to the past.
There's a good chance you've seen the date January 1, 1970 on a computer or other device, even if you weren't alive back then. You might assume this represents a significant date in computing, or that it's a random placeholder date for when a machine fails to read the time. In actuality, while the date is not special in itself, it represents an important part of how computers keep time.
Like everything in computing, the method that leads to this date is finite, meaning we'll have problems with it in the future. This all ties into a more interesting discussion of how computers (and humans) keep track of time, which is more complicated than you might think.
January 1, 1970 at 00:00 (midnight) UTC is the epoch of Unix time. An epoch refers to a specific, impactful moment, usually corresponding to the start of a timekeeping system. Unix was one of the first operating systems we would consider modern, beginning development in the late 1960s. It's the basis for many other operating systems that are known as "Unix-like," including Linux, macOS and Android. Windows is the main outlier.
When Unix was in development, its developers needed a way to keep track of time.
