Editing Chronology (section)

===Astronomical era===
{{Main|Astronomical year numbering}}
Dionysius Exiguus' Anno Domini era (which contains only calendar years ''AD'') was extended by [[Bede]] to the complete [[Christian era]] (which contains, in addition all calendar years ''BC'', but no ''year zero''). Ten centuries after Bede, the French astronomers [[Philippe de la Hire]] (in the year 1702) and [[Jacques Cassini]] (in the year 1740), purely to simplify certain calculations, put the [[Julian Date|Julian Dating System]] (proposed in the year 1583 by [[Joseph Scaliger]]) and with it an astronomical era into use, which contains a [[leap year]] zero, which precedes the year 1 (AD).<ref>Richards 2013, pp. 591-592. (Incomplete reference).</ref>