Not quite arbitrary

A couple of years ago, I wrote a blog post advocating for more public holidays during the year. I wrote the post as I was going back to work after a Christmas break, and probably feeling a little sorry for myself. I do stand by my suggestion to have more holidays through the year, regardless of the slim chance these ideas will ever be implemented.

When selecting my new holidays, I drew from a variety of sources for reasons to celebrate. Some of my choices were related to holidays and celebrations we currently observe (Christmas the obvious example). Some choices were related to events in the year of personal interest to me (it was my idea after all…). Some holidays such as for November were entirely arbitrary (and you can probably guess not the point of this new blog post). The largest group of suggested holiday celebrations (by my count seven), were holidays linked to astronomical events.

The summer and winter solstices along with the spring and autumn equinoxes are probably fairly obvious astronomical events. Slightly less obvious, Easter is roughly based on the date of the first full moon after the Spring Equinox, the Leap Day is required to adjust the calendar to account for the roughly quarter day extra on the solar year, and like Easter, the date of Chinese New Year is related to the stages of the moon.

Chinese New Year is most commonly celebrated on the second new moon after the Winter Solstice (in 2023 this occurs on the 22nd January, if you are reading this post as it is released, today!). For most people it is probably known as Chinese New Year, but might be better known as Lunar New Year as it is also celebrated in Korea, Vietnam (at least most years it is the same date) and Singapore. To my shame, I do not know much about the celebrations held across East Asia and their diaspora, but my wife and I do tend to at least mark the day, celebrating the way we do best with food.

One of the reasons I like to mark the day, beyond just the importance for millions, if not billions, of people on the planet, is it is not quite arbitrary.

Taking the fun out of life

If you value your happiness, you should never read the comments section on a news article. If you are a fan of science (who isn’t?) then you definitely should never read the comments section for articles about science and scientific discoveries. As well as a smorgasbord of out there ideas, conspiracy theories and alternative hypotheses, you will almost certainly find at least one unoriginal bore making a comment along the lines of ‘scientists take the fun out of everything’.

This comment annoys me for a variety of reasons, mostly because it is so patently not true. If anything it is the contrary, by understanding the world it becomes infinitely more fun and exciting. Science is fun, scientists can be fun. Do not read the comments section (you can read mine of course though, all my readers are lovely!).

Of course for every rule there is an exception. Step up Neil deGrasse Tyson, astrophysicist and science communicator. When most people are nursing a hangover or heading out for a bracing walk, on New Year’s Day each year Neil likes to share his thoughts on the arbitrary nature of the New Year’s celebration. This is something he has done several years in a row, with 2018 being a fairly typical example:

Not that anybody’s asked, but New Year[’]s Day on the Gregorian Calendar is a cosmically arbitrary event, carrying no Astronomical significance at all.

Neil deGrasse Tyson, 01/01/2018*

Now I should say here I don’t actually think Neil deGrasse Tyson is a curmudgeon. If anyone has heard him on Star Talk or in interviews, you will know he is a very interesting guy with a great sense of humour. My guess is his posts are an attempt at a joke and a bit of a tonic to the usual overly trite posts you get around New Year’s Day.

Regardless of the reason behind Neil’s posts, the actual content is essentially correct. New Year’s Day, at least astronomically, is entirely arbitrary. More over, New Year’s Day has not always been, well, New Year’s Day…

The idea of the 1st of January being the beginning of the year appears to have been introduced in Roman times by a certain Julius Caesar (of Julian calendar fame, amongst other things). Later Christians wanted a more religiously significant day so often started the year on Christmas Day. By the late Middle Ages the legal start of the New Year shifted to the 25th March (a legacy we still have with the British tax year starting at the beginning of April), though most people celebrated on the 1st of January. This date was legally adopted in Britain and the Empire in 1750 and has stuck there ever since.

My summary of the history of the New Year is rather potted, but hopefully it gets over the point the chosen date (and the predecessors) are essentially arbitrary. There is not much to differentiate the 1st of January from the second, third or any other day in the year beyond it being chosen by Caesar. For many holidays we celebrate or observe the situation is just the same, the actual date chosen is arbitrary, though of course will be significant for celebrants.

Once more with meaning

While many holidays are arbitrary, at least arbitrary on a cosmic scale with meaning only because with ascribe it, some holidays are at least a little less arbitrary. We’ve met most of the obvious non-arbitrary, astronomical holidays early in the post, but we can briefly run through them again here:

  • Solstices: twice yearly events when the sun appears to be at its most northerly or southerly point relative to the equator
  • Equinoxes: twice yearly events when the sun appears directly overhead at the equator
  • Full Moons and New Moons: fairly obvious I would imagine. Typically occur once a month, and you could choose how many of these different moons to celebrate
  • Solar and Lunar Eclipses: clearly not a regular annual event, but predictable and clearly spectacular
  • Comets, Conjunctions and similar: typically less frequent than eclipses, and usually less visually impressive too.

(I should say at this point, the title of this post is not quite arbitrary because even these events require us to give them some meaning, especially those lower down the list. After all, why is a full moon more important than a half moon? The reason, because we say so.)

Why do I like the idea of these events as celebration periods? Partly it is the regularity of the occurrences. Solstices and equinoxes are going to occur each year without question, at least in the likely lifespan of humanity. Comets can be predicted with fair precision. True, any one individual may note live long enough to see the comet return, but there is a good chance someone will be around.

The other part of my love for these holidays are they have meaning beyond just what it means to humans. Drop an alien on Earth and describe to them the astronomical events above, and they will surely ascribe some meaning. Sure, they might not apply the same human significance to the longest day as a celebration for example, but they will be able to appreciate the difference between the day before and the day of the solstice.

It is not just me and my imaginary alien who see meaning in astronomical days. Think about the celebrations your culture has during the year, and there is a good chance it has an astronomical basis, at least it may have done in the past. Easter and Chinese New Year we have mentioned above. Passover and Ramadan are equally related to the moon. Even the likes of Christmas being on the 25th of December are likely related to the solstice, if a little late.**


As I advocated in my post a couple of years ago, I think we need to be fitting more holidays into the calendar. If we are going to make more time for celebration in a year, why not make them a not quite arbitrary event? It has worked for civilisations for thousands of years, and continues to date significant events for billions of people.

If you want to listen to me twaddling on about Chinese New Year and more besides, click the link below for a special edition of Jigsaws 🧩 with Jamie. For those celebrating, Kung Hei Fat Choi/Gong Xi Fa Cai 恭喜發財. Wishing you all a peaceful and prosperous Year of the Rabbit.

* Usually I would link to the post directly, but it appears on a well known microblogging site which I do not want to give additional traffic given the new owner. If you are interested I am sure you can find the original post online.

** I know, I know. This is just a hypothesis and far from universally accepted, but I like it, and this is my blog post so there…

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