Q&A: Why the Year Starts on January 1st

Question: Why does the new year “start” on January 1st, rather than some other date? — RA, Greenwich, England

Answer: That’s a good question, the answer to which goes back many Moons. Fact is, the start date of the year differs from culture to culture. There’s about 40 different calendars in use today around the globe. China, for example, celebrates the new year on a variable date between January 21 and February 20.

Before you proceed, take a look at last week’s Sky Lights post. The orbit animation might help clarify my explanation here. It’s mostly about the astronomical difference between a year and a day.

Western society uses the “Gregorian Calendar,” decreed by Pope Gregory (with the help of his Jesuit astronomers) way back in 1582 AD. It was a modified version of the “Julian Calendar,” decreed by Julius Caesar in 45 BC. Both used January 1st for the start of their new year.

Of course, whatever date one chooses to start the year, one (1) year is defined as the amount of time it takes Earth to complete one (1) orbit around the Sun. The calendar start date was an arbitrary choice made by Julius Caesar. Some historians say his choice was motivated by political or religious concerns — we don’t really know for sure. Interestingly, historians note that the Roman god Janus was the god of transitions, one of his two faces looking back to the past, and the other toward the future. And the month of January is named for Janus.

By 1800, most Western societies were starting their year on January 1st. Previous to 45 BC, some countries had used the Autumnal Equinox (September 22-23) to start their year. Some used the Vernal Equinox (March 20-21). But most used the Winter Solstice (Dec 21-22). It was a confusing mix of standards in an ever-more-connected world.

The Winter Solstice was the most logical choice, since the Winter Solstice is defined as the start of Winter (north of the equator), and is also an extreme point in the Sun’s cycle of motion through the sky. Back then, time systems were much more closely synched to what the seasons were doing.

Consider that, in earlier times, it was a matter of survival to know when to plant, harvest, gather firewood, intercept migrating game or fish, and other such tasks that were synchronized to cycles of motion in the sky. There was a time in the history of our species when, if you didn’t personally find it, grow it, or hunt it … your family didn’t eat.

Bottom line: It was an arbitrary choice. So have a happy new year, whenever you choose to start it.

Q&A: Leap Year in 2012
Q&A: Holiday Decorations and Light Pollution