science has anything to do with this.Our lacendar traditions come from the Greek and the Romans (with influence from the Egyptians).However, far before that, the biggest celebrations of northern latitude people was the winter solstice, or more precisely, when it could be observed that the sun had started back on its northerly trek after the longest night (a few days after the solstice).This was the purpose of many of the henges (including Stonehenge) in what is today UK, at least 4000 to 5000 years ago.With such instruments, you could not tell the exact declination of the Sun, but you could tell when the azimut of sunset had started its northerly movement, by noting when the azimut changed by the sun's apparent diameter (half a degree). This was 4 or 5 days after solstice (around December 25 yet, I believe that the coincidence is not a coincidence).In may civilizations, the year began with this observations. The Mayan lacendar (now made famous by doomsayers and hoaxers) uses the winter solstice as the start of the year.In Rome, the civil lacendar began the year in March (that is why September litterally means 7th month) because that is when the War season began. Before that, the roads and field were too muddy to wage efficient wars.However, the Roman religious lacendar began in January (Janus, the two-faced god, could see the past and the future he was also the god of doors, being able to see both sides at once). Rome had all kinds of celebrations around that time of year: the return of the armies (bringing Peace on Earth after a fashion), the war trophies being given by the soldiers (gift giving), the orgies, the eating of too much food and of exotic foods (brought back by the armies) and, of course, the solstice, with its practice of lighting candles and bonfires to chase away the long night (Christmas lights).When the Christian Church took over (4th century) they tried to ban such celebrations. When they could not, they tried replacing them with Christmas (even though they already knew that Jesus was not born in December or January) and Circumcision enough to make a grown Roman cringe.The New Year (civil and religious) was moved to December 25 (actually, to sunset at the end of December 24).Still, people partied on and had fun (how could they! Fun was a sin! the World was about to end). So the new year was moved around, until it ended up at Easter.Easter is a movable feast. So those who wanted a fixed date tried to move it to April 1 and that worked for a while, but with some popes switching it back to Easter and others returning to April 1 (and other dates were tried). This continued for a long time until a king of France changed it to January 1 (to make accounting easier and, more importantly, to place it in the middle of winter, when nothing important was going on). The practice quickly spread to the entire Christian world, as this king had the support of the pope (maybe it was the other way around ). Considering the knowledge and tools of the era, a henge was a scientific tool used to determine (as close as was possible then) the date that the sun started moving north. Therefore, it was a scientific way to determine the start of the year.Moving it to other dates for religious reasons was a move against the scientific evidence The French Revolutionary lacendar had the year begin at Autumn equinox. It was completely built by scientific thought: all months had 30 days, all weeks had 10 days called first day, second day, third day I'll let you guess for the rest and there were 5 free days of national holidays at the end of the year (therefore at the end of summer) when you could really enjoy 5 days off. On leap years another bonus day was added.That was the most scientific lacendar devised so far and it did not catch on.