As far as the day of Jesus’s birth is concerned, Dionysius adapted the date of the festival of Sol Invictus. He did this to christianise a very popular pagan ritual, thus making the Christian celebration easier for the masses to accept. Such practice was common in the early church as Christianity struggled to supplant the ancient practices of the time. Sol Invictus had been celebrated for many centuries, by the Celts and the Romans, in a way that would be strikingly familiar to us today: decorating the houses with green branches; meals and parties; the giving and receiving of presents; etc. (who says that Christmas is an invention of our modern, commercialised times?).
Dionysius, thus, put the Nativity on December 25th 1AD. Curiously, almost at the end of the first year after Christ. He used the reigns of the emperors of Rome to calculate the date of the birth of Christ, but made two important errors in his calculations or, more accurately, an error and an omission that was not really his fault.
In other words, our modern calendar has a 5-year error built into it. One consequence is that Jesus was, as a result, illogically born several years before Christ.
Although there is some evidence that this date had been used for at least two centuries, Dionysius formalised it. Various alternative dates had been proposed for the Nativity by other authorities in the early church, but this was the one which became globally accepted.
There is another curiosity here which does not seem to have been picked up previously. Between the 16th Century and the 18th Century most of Europe changed from the Julian to the Gregorian calendar, with a jump of 10 days in the date (to be different, England adopted this change some time afterwards, whilst some countries have never adopted it and still use the old Julian calendar).
The reason for the change was the progressive shift of the seasons as too many Leap Years were added to the calendar. This was corrected when Pope Gregory decreed that centuries would only be Leap Years if divisible by 400 (i.e. 1900 was not a Leap Year, but 2000 was, although we would actually get an even better correction by only making millennium years Leap Years if divisible by 4000 so, by this rule, 2000 should not have been a Leap Year) and that the calendar should jump to correct the de-phase. In Spain, for example, this meant that the date jumped from October 4th 1582 to October 15th.
By the time that the United Kingdom got round to making the change, in 1752, the de-phase between the two calendars had reached 11 days, so the date leapt from September 2nd 1752 to September 14th 1752 when the adjustment was made.
However, despite having changed the calendar, the date of Christmas remained the same. Initially some Christians marked this by continuing to celebrate Christmas Eve on January 4th, to conserve the original date, but this practice was gradually abandoned.
However, in Russia the Julian calendar remains in use and the de-phase with the Gregorian calendar used in most of the world is now 12 days. This means that the Russian Orthodox church celebrates Christmas on January 6th each year.
Thus our December 25th is not exactly the same as Dionysius’s!
King Herod is a key player in the history of the Nativity. We know that he died shortly afterwards, but the date of his death was uncertain for some years. The clue that we have is that he died shortly after a lunar eclipse that was visible for Jericho and that he died during the lunar month between this eclipse and Passover.
Fortunately, lunar eclipses are not so common that there is a real danger of confusion. In the Jewish calendar, based on the lunar month, Passover falls in the month of Nissan, the seventh month of the year. The eclipse which fulfils the criteria was a 35% partial eclipse seen on the night of March 13th/14th 4BC. In other words, King Herod almost certainly died in late March, or early April of 4BC. Read about Passover and lunar eclipses at the time of the Nativity here.
One of the major problems in ascertaining the date of the birth of Jesus is the confusion surrounding the account in Luke’s Gospel about the census. Luke states that Quirinius was Governor of Syria at the time. Unfortunately, Quirinius did not become Governor of Syria until 6AD. This led some experts to place the Nativity as late as 7AD, completely in contradiction with Matthew’s Gospel which states that Jesus was born in times of Herod the Great. Which of the two was right? Or, could they both be right?
If we assume that Matthew was right and that Herod was still alive, the census would have had to have been before 4BC. However, it is possible that Quirinius was Governor’s legate in Syria between 6 and 5BC. Perhaps Luke, writing about a century later, confused the two posts.
Similarly, Caesar Augustus ordered censuses on three occasions: 28BC, 8BC and 14AD. The only one of these around the right time was the 8BC date, for which the order was recently located in Ankara (Turkey); the 14AD date creates yet another contradiction and the 28BC date is far too early. How can we resolve some of these contradictions? (More)
As we have seen, Dionysius picked this date for other reasons than really believing that Jesus was born on December 25th. The only real clue that we have about the true date is from Luke’s Gospel which, as we have seen, is an unreliable guide. Luke claims that there were shepherds watching over their flocks at the time of Jesus’s birth. As has been pointed out in the past, in Palestine, the winter weather is sufficiently bad – not helped by the altitude of nearly 800 metres – that the flocks would have been under shelter at this time of year. Although snow is not too common, the rain, cold and lack of fodder are sufficient to stop the animals from being left out to graze. In Spring (March-April), lambing time would oblige the shepherds to watch their flocks by night to help ewes in distress. This suggests that Jesus was born in March or April. However, it is also true that if large predators such as wolves are present, shepherds would sleep out until September.
More tenuous are two indirect clues. The first is that the inn was full. This would have been the case particularly in Passover. The second is that Jesus is referred to as “the holy lamb of God”; this, as the British expert, Colin Humphreys points out, could mean that Jesus was born at the time that the Passover lambs were selected. Both these clues would suggest a March-April date too for the first Christmas.
Bearing in mind the points made above, we can only guess at the date when Jesus was born. It was almost certainly before 4BC and the death of Herod, probably 1-2 years beforehand. It was probably in Spring. This leaves a “best guess” of March 5BC, although 6BC is a definite possibility provided that Dionysius made some additional mistake in dating (although no one has ever suggested what it might have been). An earlier date, for example, 7BC, seems much less likely. However, with so much contradictory evidence, we may never be sure that we have the right date. One happy result of this suggested date of 5BC is that Dionysius would be vindicated as the year agrees with his when the 5 year error is taken into account.