Per Mental Floss, there were a few bugs to contend with when Unix first launched back in 1971. Soon, developers smoothed things out and the epoch date on the operating system was set for January 1, 1970. That means all date and date functions performed by Unix begin from that starting point. "But wait," we hear you saying, "January 1, 1970 is not December 31, 1969 — so what gives?" The reason you might sometimes see the last day of December in 1969 rather than the first day of January, 1970 has everything to do with where in the world you are located.
That's right: The Unix operating system epoch date is not only set to January 1, 1970, it's set to January 1, 1970 GMT — Greenwich Mean Time; that's in Britain, for those keeping track (per BBC). Anywhere else in the world, and your device will read December, 31 1969 due to the time zone difference, according to Mental Floss. What causes this to sometimes happen on Unix devices is nothing more than a glitch. To fix it, simply reset the date and time on your device.
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