Why is Christmas on December 25th?

In a museum in the city of Rome (in the year 2013) I read the following theory which is also found in the German language Wikipedia.

(However, according to the Wikipedia entry it is not sure if the theory really reflects the facts.)

It is a known fact that very early Christians didn't celebrate Christmas but only other holidays - for example Easter.

When Christians started to celebrate Christmas, they were looking for a suitable date. They were choosing the date of a high Roman public holiday. And December 25th was a public holiday in Rome long before Christians started to celebrate Christmas on that day.

Because this day was a public holiday in Rome, they didn't have to go to work that day and because they didn't believe in the pagan religion, they didn't participate in the Roman ceremonies that were celebrated on that day. So they had time to celebrate the newly introduced Christian holiday.

And even more practical: In times of persecution nobody could use the fact that they did not celebrate on a pagan holiday as proof that they were Christians!

The fact that Christmas was initially only celebrated in the Roman empire on December 25th and Christians outside the Roman empire did not celebrate Christmas on December 25th makes this theory at least plausible.

I've found a very nice and detailed article discussing the relation between the Roman calendar and the date of Christmas. It is well worth to read in full, but the passage most relevant to this question is the following:

In seeking to determine the date of Christmas, critics have tended to discuss the matter in one of two ways. Adherents of "Calculation Theory" seek to demonstrate that the Nativity of Jesus can be determined independently by the chronology of the liturgical calendar. Proponents of the "History of Religions," on the other hand, tend to interpret Christmas as a substitution for the annual birth of Sol Invictus on December 25. In fact, these two approaches should not be juxtaposed and need not be mutually exclusive alternatives.

In the Julian reform of the Roman calendar, December 25, the eighth day after the Kalends of January (VIII Kal. Jan.), was recognized as the winter solstice. Nine months earlier, March 25 was the vernal equinox, the eighth day before the Kalends of April (VIII Kal. Apr.), which marked the beginning of spring. This tradition of assigning the equinoxes and solstices to the eighth day before the Kalends (the first day of the month) later was embraced by the church in its calculation of the birth date of Jesus.

Because Jesus was deemed to be perfect, his life was thought to be complete as well and to comprise a whole number of years. March 25 (the eighth Kalends of April) was believed to be the date of his conception (Annunciation) and, exactly nine months later, December 25 (the eighth Kalends of January) his Nativity. The date of Jesus' conception and crucifixion, therefore, were thought to have occurred on the same day of the year, March 25 (the eighth Kalends of April) (Tertullian, Adversus Judaeos, VIII.17; Hippolytus, Commentary on Daniel 4:23; Augustine, On the Trinity, IV.5; Dionysius Exiguus, Argumenta Paschalia, XV). Fittingly, this also was the day on which the world itself was believed to have been created.

This appears to be a rather good defense of the traditional December 25th date: Yes, Christ Was Really Born on December 25: Here’s a Defense of the Traditional Date for Christmas.

He makes three main points which I'll paraphrase as follows:

1) December 25th was not based on pagan celebrations, because Saturnalia occurs on December 22nd and the pagan feast to the Unconquered Sun that was celebrated on December 25th likely came about after Christians were celebrating Christmas on that date.

2) There are multiple references from the early to late second century about Christ's birth occurring on December 25th. Oral tradition could probably reliably indicate the birth of an important figure 1 century after the act.

3) There is a way to calculate the birth of Christ from the Bible itself by figuring out when the "course of Abias" was (which was when Zacharias was in the temple when it was announced that he would have a child, John the Baptist), and then calculating John the Baptist's birth from which Christ's birth can be calculate. This calculation gives 2 possibilities, one of which is consistent with December 25th. Also the Protoevangelium of James corroborates this hypothesis.

There are also multiple calculations done by 2nd and 3rd century writers that held the opinion he was born in the spring. But if the evidence in this article is worthwhile, then it would seem that December 25th is indeed the correct date.

December 25th was chosen as the day to celebrate Jesus' birth as a result of III- and IV-century Christians...

1. holding the notion that persons specially chosen by God - with Jesus obviously being the foremost of those persons - lived to an "integral age", meaning that they died on their birthdays,

2. calculating the Roman date of the day of Jesus' birth as either the same as the Roman date of the day of his crucifixion or, more often, as the Roman date of the day of the year of Jesus' birth (with that year being chosen according to some other criteria) whose Hebrew date was 14 Nisan, the Hebrew date of the day of Jesus' crucifixion according to the Gospel of John, eventually settling to March 25, and

3. in the IV century, switching the "integral age" notion to Jesus' conception instead of his birth, so that if his conception was reckoned to have been on March 25, his birth was reckoned to have been on December 25.

The "integral age" notion had originated in Judaism when a statement made by Moses on his last day, “I am a hundred and twenty years old this day” (Deut. 31:2), began to be interpreted in the sense that he was turning 120 years that very day, so that he had died on his birthday. BTW, note that the dates of the feasts of the Nativity and of the Assumption/Dormition of Mary in the Roman Catholic and Eastern Orthodox liturgical calendars, September 8 and August 15 respectively, are consistent with Mary living to an "integral age" according to the Hebrew calendar.

A very good presentation of this subject is:

William Tighe (2003), Calculating Christmas. The Story Behind December 25

Further details in:

Philipp Nothaft (2013), Early Christian Chronology and the Origins of the Christmas Date: In Defense of the "Calculation Theory"

There's a number of reasons to understand that Christ was conceived about 12/25 and was born at Tabernacles in the Fall.

Some believe that Nisan was the first month of the year. True enough at the time of the Exodus, but prior to that the first month was Tishri, which is in the fall. So any math that adds nine months to the March/April time frame to arrive at 12/25 has no bearing on the question.

In short, from a Scriptural time and tradition that follows, the time of creation was at the Fall equinox, not the spring time. When Passover was later instituted in Egypt, the first month became Nisan (March-April) about the Spring equinox. Some are confused by this change.

And it came to pass in the six hundredth and first year, in the first month, the first day of the month, the waters were dried up from off the earth: and Noah removed the covering of the ark, and looked, and, behold, the face of the ground was dry. Gen. 8:13

This month shall be unto you the beginning of months: it shall be the first month of the year to you. Ex. 12:2

The first month of Noah nonetheless presaged Christ at Gen.

8:4 And the ark [Christ] rested in the seventh month [Nisan], on the seventeenth day of the month [upon resurrection], upon the mountains of Ararat. Christ rested on the 17th of Nisan, having been crucified on the 14th and resurrected on the 16th.

So, Christ would have been born at Tabernacles in the Fall coinciding with creation. Nine months prior at conception is about the winter equinox.

He was circumcised on the 8th day, corresponding to the Sabbath rest of the 8th day (Lev. 23:39), the great day. Or in the New Testament corresponding to Christ's offer:

In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink. John 7:37

And the Word became flesh, and did tabernacle among us, and we beheld his glory, glory as of an only begotten of a father, full of grace and truth. John 1:14 YLT

Luke 2:8 mentions the shepherds in the fields tending their flocks. This too points away from a winter night to presumably a Fall night.

Why was 12/25 chosen instead? It would have been about the time of the angel visiting Mary. 9 months later puts us at Tabernacles.

The priestly course of Abijah (Luke 1:5, 1 Chr 24:10) may be calculated as serving the week before the summer solstice. John was then conceived the next week. Thus this gives us the 6 months earlier at the summer solstice (John) from the winter equinox (Christ) and was born 9 months later at Passover (John).

In type (physical mimicking spiritual), John said He must increase, I must decrease (John 3:30). The solstices were the change of seasons. Thus Christ was conceived about 12/25.

Over the centuries, there had been a concerted effort to divest Christianity from various Jewish roots and understandings. Realities lost led to man-made traditions. It is true enough a number of pagan celebrations occurred about the winter solstice, like the birth of Sol Invictus. Subsequently, 12/25 was incorrectly chosen as the birth, rather than the conception of Christ. But tradition and scripture point to Christ's birth at Tabernacles in the fall.

The exact day for the birth of Jesus is not known. You can find a lot of info on Wikipedia, with references. The most interesting for this question might be:

The precise day of Jesus' birth, which some historians place between 7 and 2 BC, is unknown. In the early-to-mid 4th century, Western Christianity first placed Christmas on December 25, a date later adopted also in the East. Theories advanced to explain that choice include that it falls exactly nine months after the Christian celebration of the Annunciation, or that it was selected to coincide with either the date of the Roman winter solstice or of an ancient pagan winter festival in order to stamp out these celebrations and replace them with a Christian one.

(http://en.wikipedia.org/wiki/Christmas)

"Chronograph" ¹ – a document dating to 354 AD ² in Rome: This was a list of martyrs and their birth dates, and a list of bishops of Rome and their birth dates. The Chronograph lists these dates (birth dates) in calendar order. The first date listed is the "8th of Kalens of January" ("Kalens" is used to refer to the first of a month – putting a number in front of it counts backward.) This translates to our December 25th. The notation in the Chronograph is that this is the birth of Christ in Bethlehem.

On the list, the last two bishops were added on apparently after the list was otherwise complete (dates out of order). The first bishop had died in 336 AD. Thus, it is probable that this list dates to 336 AD.

In 303 AD, under Diocletian, was the "last" persecution of the church. After this time of persecution, lapsed Christians-those who had recanted under persecution, were allowed back into the church (upon profession). There was a group called the Donatists that disagreed with this practice – they felt that the lapsed Christians should not be allowed to rejoin the church. The Donatists broke away from the church.

Augustine opposed the Donatists. He noted ³ that "the Donatists do not celebrate Epiphany", which was started as a celebration of the baptism of Jesus. Apparently, the Donatists celebrated Christmas – Augustine doesn’t say that they didn’t. This would push the celebration of Christmas back to before 311 – the time of the Donatist split.

A document called "De Pascha Computus" – calculating the date of Passover. The document also lays out a scheme to calculate the birth of Jesus. The calculation fell on March 28 of our calendar.

There were several assumptions made in calculating this date – assumptions from Jewish tradition. Jewish tradition held that the time of the Passover celebration was also the time of the beginning of creation. The sun, moon, and stars were created on the 4th day of creation. Malachi 4:2 refers to the "Sun of Righteousness" (referring to Christ). The reasoning is that it was symbolically fitting for March 28th to be the birth of the light of the world.

Though use of December 25th is not supported, yet the plan of celebrating birthday of Jesus was prevailing around 243 AD.

Note that even as early as the 12th century, it was thought that December 25th was co-opted from the pagans. EVEN IF it was co-opted, it was infused with new meaning by the best theologians of the time. But there is good evidence that a date of December 25th is true – it just happened to fall on the winter solstice. Early Christians believed that December 25 was the true day. It is likely that the early Christians would try to identify the birth day of their Saviour.

"De Solstitiis" – a North African document from the 300’s attempts to determine the date of Christ’s birth entirely from the evidence given in Scripture. It assumes a date of March 25th for Christ’s death (Passover).

The reasoning begins from the conception of John the Baptist. The angel made the announcement to Zechariah. Zechariah completes his "time of service" and returns home. (Luke 1:23-24) The time of service is complete in the fall of the year (when the Jewish year changes). When Zechariah returns home, Elizabeth conceives John. This is around the time of the Fall Equinox.

The announcement to Mary comes in Elizabeth’s six month – this would be about the Spring Equinox. This also happens to be Passover – the date of the death of Christ – March 25th (by the Julian calendar).

Birth of John – 9 months after Fall – Summer solstice.
Birth of Jesus – 9 months after Spring Equinox – puts it at the Winter Solstice – on (or about) December 25th (Julian calendar).

This reasoning is based on the presumption of the conception of John the Baptist.

This line of reasoning is adopted by Augustine – he notes that the conception and crucifixion occurred on the same day. Also accepted by John Chrysostum – in the 380’s, he reproduces this reasoning in the east – using the common eastern calendar – winds up 2 weeks off – January 6 for the birth of Jesus and April 6 for the death of Jesus. Augustine and Chrysostum promoted the celebration of December 25 because it is believed to be the actual date.

Since Clement of Alexandria was in the "east," we can assume that he used the eastern, or Egyptian, calendar in his calculations. He arrived at a date of January 6th (according to our calendar). This is the reason for the eastern church using Jan 6 and resisting December 25.

Also, Epiphanius (died 403 AD) in Palestine does the same calculation as in De Solstitiis, using the eastern calendar for dates, and also winds up two weeks later than December 25.

All these calculations have nothing to do with pagan festivals or equinoxes and solstices. (Jan 6th is two weeks after the winter solstice.)

Let me add here: We do not find any historical date in Bible, may be for obvious reason since the bottom line in Bible was to deliver a message of Salvation and not a historical record of events that took place. Notwithstanding this, there is always an urge in humans to remember and celebrate those events, which influenced their destiny. That urge gradually led the early Christian to commemorate all those sacred events that took place in life of our Lord as remembrance and veneration of our Lord. Savior and Emmanuel (God with us) spent His life as one of us and like us among us the earthly creatures. His birth, death and whatever mighty deeds He carried out are by no means any ordinary events.

Suppose we were those unfortunate who never knew the birth date of one of our parents, we would somehow try to decipher the probable date from whatever source. As such not knowing the date would not stop us from celebrating this event. In similar scenario, we were unfortunate not to know the exact date of our Lord's birth and in absence of any exact dates in Bible, it is not at all a SIN to fix appropriate day for this event in a year to give us opportunity to commemorate them in honour of our Lord. If one ponders it in an unbiased mind, it is not an issue at all whether Christian celebrate the Christmas on 25 December or 6 th of January as some do. What is important is we need one day to celebrate the day of birth of our Savior. Whether it is the date which coincides with the birth day of some pagan god or with birth of any other founder of any other present day religion is immaterial for any true and broad minded Christian. Celebrating a birthday by no means can be considered as Pagan.

Because paganism was prevailing during the early years of Christianity, just by relating any event in Christian practice to a pagan practice is easiest way to create doubt in minds of believers by saying that it relates to pagan practice.

¹ _{The Chronography of 354. Introduction to the online edition}

² _{The Manuscripts of the "Chronography/Calendar of 354 A.D."}

³ _{Augustine on Baptism Against the Donatists, Book 6}