The year when Jesus was born is the beginning of the calendar year, and the starting point is 1. In julian calendar and Gregorian calendar, the day after the birth of Jesus is called Anodomeni. Before the birth of Christ, it was called BC, but in order to dilute the religious color and avoid the antipathy of non-Christians, most modern scholars changed their names to AD (abbreviated as C.E.) and BC (abbreviated as B.C.E).

After A.D., that is, the Gregorian era, it was originally called the Christian calendar, also known as the western calendar or Gregorian calendar. The method of calculating the year originated from western society. A calendar invented by Italian doctor and philosopher aloysius Lilius is a reform of julian calendar. 1582, Pope Gregory XIII approved the bill.

Extended data:

Matters needing attention when calculating AD:

AD, the name of the calendar method, is used in the calendar system. The calendar takes the birth of Jesus as the first year of AD and is named after the first year of BC. AD20 19 is 20 19 in the first year.

It is worth noting that although 0 is a natural number, there is no such thing as 0 BC or 0 AD. The year after BC 1 year is AD 1 year, which is the first year. Although the number of BC years is backward, the latter figure is smaller than the previous one. For example, the Western Han Dynasty was founded in 202 BC and later than the Qin Dynasty in 22 1 year BC, but the specific month, or positive number, of each year is the same after 1 month and1February, and the date is the same, after the first day and the fifteenth day.