Epoch time and Epoch time milestone

The Unix epoch (also known as Unix Time Stamp) is the representation of time as the number of non-leap seconds since 00:00:00 UTC on January 1, 1970. It is introduced by Unix operating  system, , standardised in POSIX.  The clock is used not just by Unix, but also by Linux, Java, JavaScript, Mac OS X, and various other technologies. In the fields of chronology and periodization, an epoch means an instant in time chosen as [...]