You can use this online tool to convert Unix Timestamps to dates and vice-versa.
From Wikipedia:
Unix time, or POSIX time, is a system for describing points in time, defined as the number of seconds elapsed since midnight proleptic 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 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 the times it represents are UTC but it has no way of representing UTC leap seconds (e.g. December 31, 1998 23:59:60).