23711 2013-11-03 18:18:46 +0000 "The present form of UTC, with leap seconds, is defined only from 1 January 1972 onwards." https://en.wikipedia.org/wiki/Unix_time 2013-11-13 22:59:11 +0000 1 1 1 Unclassified WHATWG HTML unspecified Other other RESOLVED WORKSFORME http://www.whatwg.org/specs/web-apps/current-work/#date-and-time-state-(type=datetime) P3 normal Unsorted 1 contributor ian ian mike contributor oldest_to_newest 95739 0 contributor 2013-11-03 18:18:46 +0000 Specification: http://www.whatwg.org/specs/web-apps/current-work/multipage/states-of-the-type-attribute.html Multipage: http://www.whatwg.org/C#date-and-time-state-(type=datetime) Complete: http://www.whatwg.org/c#date-and-time-state-(type=datetime) Referrer: http://www.whatwg.org/specs/web-apps/current-work/multipage/ Comment: "The present form of UTC, with leap seconds, is defined only from 1 January 1972 onwards." https://en.wikipedia.org/wiki/Unix_time Posted from: 75.131.222.221 User agent: DN Explorer/2.4 (20130210) DNIAS/2.4 (20130210) 95773 1 ian 2013-11-04 21:56:59 +0000 That's why the spec says: "Times in dates before the formation of UTC in the mid twentieth century must be expressed and interpreted in terms of UT1 (contemporary Earth solar time at the 0° longitude), not UTC (the approximation of UT1 that ticks in SI seconds). Time before the formation of time zones must be expressed and interpeted as UT1 times with explicit time zones that approximate the contemporary difference between the appropriate local time and the time observed at the location of Greenwich, London."