by ryan on October 21, 2011
“All operating systems know when they were born. Their internal clocks start counting from then, so they can calculate the date and time in the future. It is unclear whether it was Mr Ritchie or Mr Thompson who set the so-called start Unix time at January 1st, 1970. That moment came to be known as the epoch. Mr Ritchie helped bring it about. And with it, he ushered in a new era.”
from the economist article about dennis
and every time you calculate time on a unix machine you are using one big number that is down to the millisecond of how long it has been since the epoch.