UnixTime (also known as POSIX time or Epoch time) is a system for describing instants in time, defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC), Thursday, 1 January 1970. It is used or returned by a number of Functions.
Example: 1451492206 – the corresponding ISO 8601 formatted date is 2015-12-30T16:16:46Z