Let me explain.
Many of you have probably heard of time referred to as UTC (Coordinated Universal Time). Many of us (including me, before today), never really give much thought to how time is calculated, and still think that GMT (Greenwich Mean Time) still refers to the time in Greenwich, England. That was true from 1884 – January 1, 1972.
Instead, in 1972, UTC replaced GMT as the basis for the primary reference time.
Why are you telling me all of this?
Because Epoch (UNIX) time was created and based on the same timing structures. When it was created, they started with January 1, 1970 as the “beginning” of Epoch time. It is based on the belief that there are 86,400 seconds in each day. (60 seconds x 60 minutes x 24 hours = 86,400)
On Friday, February 13, 2009 at 6:31:30 PM EST, we reach a unique number of seconds in Unix time.
You can see the countdown here: http://www.coolepochcountdown.com/