The Story of the World’s Calendars: Keeping Track of Time

October, 2017

The holidays aren’t always easy to plan for, but if it’s Christian Christmas you celebrate, at least it’s easy to remember when it is: December 25 (January 7 for Orthodox Christians), year after year. If, however, you or any of your friends follow non-Christian faiths, or if you’ve ever taken a close look at the holidays that come pre-loaded on standard calendars, you might have noticed that the holidays and celebrations of some religions tend to jump around a bit. The Jewish celebration of Hanukah, for example, started on December 24 last year, while this year it will begin on December 12. It might seem odd that these non-Christian holidays don’t align to the calendar properly, but a closer look reveals that they align perfectly well—just to a differentcalendar than the one most of us use. There are two main calendar systems in the world, and while our Western calendar calculates time according to our orbit around the sun, there are many others that calculate time according to the phases of the moon. Both systems have rich histories and can tell us quite a bit about not only ourselves, but our friends and neighbours as well.

Our Solar Culture

Our Western calendar traces its origins back to ancient Egypt. At one very specific time of the solar year, almost like clockwork, the Nile River was known to flood and cover the main Egyptian river valley with nutrient-rich sediment. This annual event allowed the Egyptians to produce crops that most desert cultures could only dream of. It was so important in fact, that this event formed the basis of the Egyptian calendar. Everyone in Egypt knew that once, every 365 days, when the sun rose along a specific spot on the horizon, the river would flood. If farmers weren’t ready for this, they wouldn’t be able to grow enough food to satisfy the whole population. For the Egyptians, keeping track of the Earth’s orbit around the sun (or, as they would have seen it, the sun’s orbit around the Earth) took on a spiritual significance. Adhering to the solar calendar was a matter of survival. As a result, Egyptian holidays and feast days were set to correspond to the yearly variations of the sun’s position in the sky.

It wasn’t long before the Romans, history’s great imitators, adopted the Egyptian calendar for their own use. Even though the Romans didn’t have a Nile of their own, the Egyptians showed them that studying the sun could lead to other rewards. With a solar calendar, they could predict the seasons. They would know precisely when the rains were coming and when the winter would start. With this knowledge, they could maximize their agricultural output, support a large population base and even plan their military campaigns during strategic seasons. When their campaigns led them to Greece, they partially adopted the Greeks’ lunar calendar as well, further dividing their 365-day calendar into 12 months (or moon-ths, as the word was originally pronounced in English), which corresponded roughly with the phases of the moon. Just like the Egyptians before them, the Romans found that the solar calendar brought them a great deal of prosperity. It wasn’t long before they began matching their feast days with specific dates on the calendar as a way to both mark and celebrate their good fortune.

In the year 45 BCE, Julius Caesar further refined this calendar into what he called the Julian Calendar (he named it after himself). In this calendar, Caesar created the 7-day week, the month of July (also named after himself) and the concept of the leap year, which made up for the fact that a solar year isn’t actually 365 days, as was previously thought, but 365.24 days. When Christianity was legalized in Rome 358 years later, Caesar’s 7-day week happened to correspond perfectly to the traditional 7-day week of the Christian Bible, and new converts discovered that their new Christian holidays, which had previously followed the Jewish lunar model, could easily be mapped onto the Julian Calendar. As the Roman Empire continued to expand, Christian missionaries started spreading the word of God to all corners of Europe, and they brought the solar calendar along with them.

The final change to our solar calendar came from Pope Gregory in the year 1582. Gregory’s changes to the Julian calendar brought it even closer in line with the realities of our orbit around the sun by further refining the concept of the leap year. Caesar had miscalculated the length of a year by 11 minutes. This doesn’t sound like much, but a loss of 11 minutes per year over a millennium can really start to add up. By Gregory’s time, seasons no longer matched the climate that they were supposed to represent. More importantly though, the Gregorian Calendar, as it became known, allowed the church to more accurately calculate the date that Easter should be celebrated, which had fallen out of sync with its traditional anchor point, the Spring Equinox.

We’re still using the Gregorian Calendar today, and even though our society has become more secular and multi-cultural than it was in Gregory’s day, our calendar still acts as a record of society’s Christian past.

The Lunar Method

Lunar Calendars follow the same logic as their solar counterparts, but instead of calculating time in 365.24-day solar years, they measure time in a series of 29.5-day lunar months. The main benefit of solar calendars comes from their ability to predict seasonal changes. However, in equatorial areas of the world that experience low seasonal variation, the sun isn’t as useful as the moon when it comes to telling time.

With all of our bright city lights, we don’t often take notice of the moon and its phases. But in a pre-electric society, the moon was far more noticeable. A lot can be seen under the light of a full moon. Early humans could hunt, travel, watch for danger or even just socialize late into the night. Under a new moon however, nights became a lot more frightening and unknowable. By knowing which phase the moon would be in at certain times, early lunar cultures were able to maximize their food production and protect themselves much more easily than they would have been able to with solar observation. Just like their solar counterparts, lunar calendars allowed ancient peoples to make predictions and learn how to make the best use of their environments. And, just like our society’s solar predecessors, the lunar cultures of the world were quick to fit their feast days and celebrations into their lunar model.

The Hebrew, Islamic, Hindu, Buddhist and Chinese calendars are all lunar-based and traditionally cycle between 29 and 30-day months (to make up for that extra half day in the month). In the same way that our months correspond roughly with the phases of the moon, the months of a lunar calendar are typically grouped in sets of 12 or 13 so that they roughly correspond to a solar year. Since a 365.4-day solar year isn’t divisible by a 29.5-day lunar month, neither system can perfectly represent the other, and solar and lunar calendars will never quite align perfectly. This is why, from a solar perspective, holidays like Ramadan, Diwali, or Chinese New Year seem to be inconsistent from year to year. From a lunar perspective though, our stable Christmas season seems just as variable.

Creative Alternatives

The Earth is a big place that is full of lots of different ideas. As such, there are many cultures that don’t make use of either the sun or the moon to measure time. Early cultures calculated time based on what made the most sense in their own environment, but not all of those environmental cues can be found overhead. Over the millennia, different cultures have come up with some pretty incredible ways to measure time.

In the Arctic Circle, the sun does not rise for a period of four months, dusk and dawn last for three weeks each and for the rest of the year, the sun never sets. The brightness of the aurora, coupled with the sometimes-blinding snow means that the moon isn’t always a reliable timepiece either. The Inuit found a way to calculate time all the same, by watching certain stars rise and set along the horizon during the dark months of the year.

The Coast Salish people of what is now British Columbia knew of the lunar model, but often found it less reliable than studying the migratory patterns of the fish that made up the majority of their diet. Certain types of salmon swim upstream at only certain times of year, and this fish-based calendar allowed them to prosper in ways that studying the sky never could.

During the French Revolution, the new government wanted to distance itself from the Catholic Church and its royalist history. It started by reforming the calendar into what was thought to be the perfect mathematical representation of time. Each year was divided into 12 months of 30 days each, wherein each week contained 10 days. Unfortunately for the revolutionaries, this hyper-efficient, mathematical calendar never really caught on, and France reverted back to the traditional Gregorian Calendar.

Perhaps most imaginative of all of Earth’s calendars was the ancient Mayan calendar. The Mayans knew of the solar model and the lunar model, but dismissed both. Instead, they used their incredibly advanced astronomy skills to study the phases of the planet Venus in the same way that lunar cultures would study the phases of the moon—all without a telescope. Venus was so important to their faith that they based an entire religious calendar around it.

The Perfect Model

Over the centuries, most of the world’s calendars have shifted and changed in order to make use of new information, and oftentimes this involves a blending of solar and lunar models, as well as seasonal information. While we still draw distinctions between different systems of timekeeping, the majority of the world’s calendars are now technically “lunisolar,” meaning that they take attributes from both systems. The Christian holiday Easter, for example, always falls on the first Sunday following the first full moon after the Spring Equinox. Easter isn’t purely a solar holiday, but it is not fully a lunar holiday either. It is a functional blending of the two.

Timekeeping is such an imprecise art that both solar and lunar calendars end up having their fair share of imperfections. There have been many attempts to create mathematical calendars, like the one used in the French Revolution, but while these ultra-logical models do remove human inefficiencies, they always end up removing the humanity of the calendar as well. Calendars do measure time, but they also preserve our heritage, allowing us a glimpse at the values that our ancestors found important, and the worries that they had. While we no longer rely on these solar and lunar models for our survival, the traditions associated with them are so strong that it’s hard to imagine trading our calendars in for a more efficient model. Our early ancestors were quick to figure out the best timekeeping method, and we’ve all been using it ever since. Time, ultimately, is what we make of it, which makes the perfect calendar whichever model works best for you.  t8n


Fun Fact

Despite there being billions of suns and billions of moons in our galaxy, we still refer to our sun and moon as “the” sun and “the” moon, as if they were the only ones. In Latin, their proper names are Sol and Luna, which form the basis for the terms solar and lunar.


Did You Know?

In addition to recording time in different ways, the calendars of the world all have different start dates. While it is the year 2017 to us, it is 1439 in the Islamic calendar, 2560 to Buddhists and 5775 according to the Jewish tradition.



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