The Date Of Christmas

I've said this many times before, but astronomy effects our daily lives in ways of which we're often unaware. For example, you may be surprised to find that the date of Christmas is almost certainly down to our ancient forebears' astronomical endeavours.

Imagine you’re a prehistoric farmer. You would have little understanding of what we today call science. But you would almost certainly know a lot about the motion of the Sun, Moon, stars and planets around the sky. In fact, these motions would be very important to you. Why? Because they mark the passage of the seasons and the seasons dictate what sustenance is available to humankind. Your survival depends on them. If you want your crops to grow, your livestock to survive, your hunt to be a success, you need a good knowledge of where you are in the yearly cycle of life. And it is the skies which give you that knowledge.

So, here's the science bit (as people annoyingly say!). In the morning, the Sun rises in the East, travels up and across the sky before setting in the West. This is a result of the Earth spinning once a day on its axis. But throughout the year the Sun rises and sets at a different place on the horizon. This is a result of the tilt that the Earth's rotation axis makes with the plane of its orbit around the Sun. In the Northern Hemisphere, in the summer, the Sun rises in the north-east and sets in the north-west. The Sun’s track across the sky is therefore quite long and it reaches very high in the sky. This makes the summer days long and warm. But in the winter the Sun rises in the south-east and sets in the south-west. It doesn’t take long to cross the sky and it doesn’t rise very high. That’s why the winter days are short and cold.

On midsummer’s day, that is, June 21^st, the Sun rises at its most northerly point so that the day is the longest in the year. Astronomers call this time the summer solstice (literally 'stationary Sun'). After the summer solstice the Sun rises steadily further south and the days get shorter and shorter. Midwinter’s day, December 21^st, is the day the Sun rises at its most southerly point and so is the year’s shortest day. The halfway points for the Sun occur on or about the 21^st of March and 21^st September. These are when the days and nights are of equal length and are called the spring and autumn equinoxes (literally 'equal night').

For our prehistoric farmer these facts would be well known. In fact, it is believed that many prehistoric sites, like Stonehenge, were built to follow the changing seasons from the rising and setting of the Sun. The two solstices, summer and winter, were very important festivals. In winter, the ancient peoples would celebrate the winter solstice because it marked the time when the Sun would turn back from its ominous journey to the south, which made the land barren, cold and dark. Major festivals were held to give thanks that the lengthening days would soon see an end to hardship and frugality. Although today is the winter solstice (and I'm sure pagans everywhere are celebrating!), most people have thoughts of another imminent festival on their minds.

But, is it merely a coincidence that the modern Christmas celebrations occur near the winter solstice? Firstly there is no indication in any of the gospels for the date of Christ's birth. However, early Christians (by the 2nd century AD) seem to have accepted the date of Jesus' conception (the Annunciation) as 25^th March, which would naturally imply a birth date around 25^th December. But, originally, the Christian Church did not celebrate the birth of Christ at all, but instead his 'baptism' during which he was declared the Son of God. This feast, called Epiphany, was held on 6^th January. But at some stage in the first few centuries AD a tradition seems to have grown up involving the celebration of Christ's birth. The first time Christmas is recorded as being celebrated on 25^th December is during the reign of Emperor Constantine (the first Christian Roman Emperor) in 336AD. This date was later adopted by both the Western and Eastern branches of the Christian Church. The Council of Tours in 567AD declared the time between Christmas and Epiphany to be a unified festival, giving both dates equal importance and providing us with our 'twelve days of Christmas'. In the Middle Ages Epiphany was the major religious festival of the year rather than Christmas. Of course, Epiphany is still an important celebration in the Christian Church. It is associated with the visit of the Magi (the three wise men) to the infant Jesus and, consequently, in some countries Epiphany is the date for the giving of gifts instead of Christmas Day.

But modern scholars are somewhat suspicious that Christmas occurs so close to an important ancient festival. One school of thought suggests that the early Christian Church may have attached the Christmas festival to the already prevalent mid-winter festivals such as the Roman 'Saturnalia' and 'Dies Natalis Solis Invicti'. It is evident that many of the things we think of as Christmas traditions are in fact remnants of those pagan festivals. This includes Christmas trees, Christmas carols, evergreens such as ivy, holly and mistletoe, lights, merrymaking and the giving of gifts. Even the word 'Yule', synonymous with Christmas for most of the English-speaking world, comes from the Anglo-Saxon word 'Geola', their name for the pagan mid-winter festival (also celebrated throughout Scandinavia). Not surprisingly, this pagan association has seen the observance of Christmas festivities banned in some countries over the years! Today, we have the Victorians to blame for many of our modern Christmas traditions and how someone called 'Santa' got wrapped up in all of this is an entirely different story!

So, when was the actual birth of Christ? Well, we may never know. But there are good reasons to suppose it wasn't on 25^th December. As the gospels say, the shepherds were tending their flocks on the hills, something they wouldn't be doing in mid-winter, even in the Holy Lands! Some scholars believe September-October might be appropriate since the Jewish festival of 'Sukkot' occurs at this time when many Jews would visit Jerusalem. The increase in population would mean the inns would be full and it would be the perfect time to conduct a census of the people.

Whatever the case, it is unlikely Christmas Day is the true date of Christ's birth. It's more likely a result of our ancestors in-depth understanding of celestial motions and how that cosmic dance determines the cycle of birth, life and death. And that understanding comes from watching the sky, just as astronomers do today.

Incidentally, the exact time of today's winter solstice (when the Earth's North Pole is tilted furthest away from the Sun) is 23:03 UT (or 11:03PM GMT). From that time onward, the days are getting longer! Hurrah! Must be time for a celebratory drink!