In case anyone thought it should be December 25, zero A.D., in fact historians ignore the possible year zero and date events in either 1 A.D. or 1 B.C.; astronomy confusingly adopted a year zero so if you consult an astronomical table and see an event in any year B.C. then to a historian that would be one year less (earlier), so for example if there was a planetary conjunction claimed as possible “star of David” that an astronomer said was in 3 B.C., to a historian that would be in 4 B.C. ... anything that happened in the year zero would be in 1 B.C. for historical reference.
I have read estimates of the birth of Jesus between 6 and 3 B.C. based on what is actually known about the historical context (most important of those being the actual timing of the relevant Roman census and the later death of Herod).
By the year 1 A.D. when historians would say the first Dec 25th took place, Jesus was probably approaching his fifth or even sixth birthday. This has a practical significance in that estimates of the year of the crucifixion (30 and 33 A.D. are the two most quoted) are probably more accurate which means Jesus was approaching forty at that time, not in his early thirties. That gives a longer interval of time possible for His active ministry since it would appear that the spiritual baptism was an event in his young adult years, if He were 21 for example that would have been in 16-17 A.D. not 21 A.D. ... a full decade and a half before the crucifixion.
No year zero exists, or can exist, mathematically speaking.
The best way to conceive of this is through the use of a number line.
A dot in the center, a first ray extending from the center dot to the right, and a second ray extending from the center dot to the left.
Hash marks are not labeled with numerals but instead merely indicate the transition between years.
Braces labeled with numerals indicate the span of a year, a decade, a century, a millennium, etc. A year is represented in this way as a certain standard distance along the number line.
The first “braced” span between the center dot and the nearest hashmark, one to the left of the center dot, and the other to the right of the center dot, is labeled with the numeral “1”.
The last year in the first millennium was year 1000. The first year in the second millennium was year 1001.
Similarly, the last year in the second millennium was year 2000. The first year in the second millennium was year 2001.
The last year of the twentieth century, for example, was the year 2000. Then, the new year’s eve ball dropped and we found ourselves, on January 1, 2001, in the twenty-first century.
The New York Times celebrated the arrival of the twentieth century in the paper it published on January 1, 1901. Nobody argued at the time with the mathematics the New York Times used to support its editorial decision to commemorate the arrival of the twentieth century.
The New York Times strangely allowed January 1, 2001 to arrive with no such fanfare within the pages of its newspaper, despite the arrival of not only a new century, but a new millennium. Why do you think this was?
Don’t bother. This Guy will answer:
Metastasizing societal ignorance and stupidity.
There is not and never was any such thing as a year zero.