The number you see in the title is also known as Epoch (UNIX) time. When Epoch time was created, they set the "beginning" to January 1, 1970. Like the Year 2000 bug, this was done to save storage space. Because if all time was based around the assumption that January 1, 1970 is equal to zero, and every second past that represents the date since 1/1/1970 00:00:00, then they could store relatively small numbers for calculating a date and time and easy calculate the date since the "beginning of computer time" with simple math. This also allowed them to calculate how much time has passed by just taking the difference of the two numbers and running it though the same simple math. However the time 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, today, 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/