So that people can represent times that occurred before 1970? You could try adjusting the epoch to the estimated age of the universe, but then you run into cale

So that people can represent times that occurred before 1970? You could try adjusting the epoch to the estimated age of the universe, but then you run into calendar issues (proleptic Gregorian?), have huge constants in the common case (Julian Days are not fun to work with), and still end up with issues if the estimate is ever revised upward.