History of dating in 1818
Dionysius Exiguus (about the year 500) was the founder of that era, which is nowadays the most widespread dating system on earth.
An epoch is the date (year usually) when an era begins. It was used to identify the Roman year by a few Roman historians.
Unrelated dating methods help reinforce a chronology, an axiom of corroborative evidence.
Ideally, archaeological materials used for dating a site should complement each other and provide a means of cross-checking.
Dendrochronology estimates the age of trees by correlation of the various growth rings in their wood to known year-by-year reference sequences in the region to reflect year-to-year climatic variation.
Dendrochronology is used in turn as a calibration reference for radiocarbon dating curves.
To place all the events on the same time scale, Eusebius used an Anno Mundi (A.Modern historians use it much more frequently than the Romans themselves did; the dominant method of identifying Roman years was to name the two consuls who held office that year.Before the advent of the modern critical edition of historical Roman works, AUC was indiscriminately added to them by earlier editors, making it appear more widely used than it actually was.(AD 1 = AUC 754.) 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 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).