Unix time (also known as Epoch time, POSIX time, seconds since the Epoch, or UNIX Epoch time) is a system for describing a point in time. It is the number of seconds that have elapsed since the Unix epoch, minus leap seconds. The epoch is Unix time 0 (midnight 1/1/1970), but 'epoch' is often used as a synonym for Unix time.
Unix time is widely used in operating systems and file formats. A Unix time number can be represented in any form capable of representing numbers. In some applications the number is simply represented textually as a string of decimal digits.