Unix time, or POSIX time, is a system for describing points in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time (UTC) of January 1, 1970, not counting leap seconds. It is widely used not only on Unix-like operating systems but also in many other computing systems. It is neither a linear representation of time nor a true representation of UTC (though it is frequently mistaken for both) as the times it represents are UTC but it has no way of representing UTC leap seconds (e.g. 1998-12-31 23:59:60).
“At 11:31:30pm UTC on Feb 13, 2009, Unix time will reach 1,234,567,890.
Where will you be at this momentous second?” – from Bell Labs
You can use the following perl command to find out when the Epoch time reading will be 123456789 in your time zone
perl -e 'print scalar localtime(1234567890),"\n";'