Origin of calendar dating
To correct this, the Gregorian calendar was introduced by Papal decree in 1582, when ten days were dropped, so that September 4 was followed by September 15.
The Sumerian administration also needed a time unit comprising the whole agricultural cycle; for example, from the delivery of new barley and the settling of pertinent accounts to the next crop.This fluctuating and discontinuous year was not precise enough for the meticulous accounting of Sumerian scribes, who by 2400 BC already used the schematic year of 30 12 = 360 days.At about the same time, the idea of a royal year took precise shape, beginning probably at the time of barley harvest, when the king celebrated the new (agricultural) year by offering first fruits to gods in expectation of their blessings for the year.This financial year began about two months after barley cutting.For other purposes, a year began before or with the harvest.Unfortunately, while Caesar's calendar was almost accurate, it wasn't quite accurate enough because the tropical year is not 365 days and 6 hours (365.25 days), but is approximately 365 days 5 hours 48 minutes, and 46 seconds (365.242199 days).
Therefore, the calendar of Julius Caesar was 11 minutes and 14 seconds too slow.
The cause of this calendrical confusion was the over 1,600 year-old Julian calendar, established by Julius Caesar in the year 46 BCE.
Julius Caesar took control over the chaotic Roman calendar, which was being exploited by politicians and others with the haphazard addition of days or months.
As former UN General Secretary Kofi Annan put it in a statement marking the turn of the millennium: The Christian calendar no longer belongs exclusively to Christians.' For some, these are fighting words: the Southern Baptist Convention resolved, also in 2000, to resist the 'revisionism' implicit in the CE/BCEsystem and to retain AD 'as a reminder to those in this secular age ... The AD/BC chronology is not so ancient as some proponents suppose; nor is the CE/BCE system so recent.
For the first five centuries of their religion, Christians marked time according to local conventions, usually from the legendary foundation of Rome (753 BC), or from the Diocletian reforms (284 AD).
Caesar's calendar was normally 365 days long but included an extra day (a leap day) every four years to account for the extra one-quarter of a day.