Temporal Reference System Unix Time https://www.commoncoreontologies.org/InformationEntityOntology Unix Time is a Temporal Reference System for describing a point in time, defined as the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC) Thursday, 1 January 1970 minus the number of leap seconds that have taken place since then. (See: https://en.wikipedia.org/wiki/Unix_time)