Difference between Unix Time and UTC time

 

Simply speaking, Coordinated Universal Time (abbreviated
UTC) is a timming methon that keeps the days synchronized with
the rotation of the Earth (or Universal Time). And because of the magical
rotation of the earth, the scaling of UTC will be kind of
irregular, therefore leap second is invented to
calibrate.

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 used widely, not only in Unix-like operating
systems, but also in many other computing systems and file formats. It is
neither a linear representation of time nor a true representation of
UTC (though it is frequently mistaken for both), as it cannot
unambiguously represent UTC leap seconds (e.g. December 31,
1998 23:59:60), although otherwise the times it represents are
UTC. In a word, Unix time is an encoding of
UTC.