What is a calendar for?
The Tower of Winds said to be, among other things, a calendar.
The need for a calendar is something that gets assumed. People have to have calendars. Whether you’re an astronomer like Patrick Moore, or a classicist like Emma Gee you have to have calendars to know when to plant crops or when to harvest. But is this really the case? If you look at a lot of early calendars then you find that, if you followed them, you’d have a recipe for famine. So what are calendars for? The earliest calendars appear to be lunar. The period of a lunation, usually measured by the time from one New Moon to the next, was a month and this was used to break up the year. It’s a simple system, so long as you don’t have people arguing over whether they really can see the wafer thin crescent of a New Moon.
Moon, a few days old. Photo by Atanas.
The problem is that the lunar cycle doesn’t neatly match the solar cycle. If you have twelve months in a year then the year finishes eleven days too early in comparison with the Sun. If you have thirteen months then its eighteen or so days too long. This is a problem because it’s the Sun that creates the seasons, not the Moon. Without inserting extra months, intercalary months, your calendar would slip out of sync with the sun rapidly. After just seventeen years midwinter months would be in the height of summer and vice versa. So the ancient Greeks used to solve the problem by having either twelve of thirteen months in a year. In the long run this is accurate, but from year to year this eleven day gap still makes a lot of difference. It means that if a Greek month was in the equivalent time of year as July by our calendar then it could start as early as mid-June or finish as late as mid-August. Our months are defined by the Sun, so they always happen, within a day or so, at the same time in the Earth’s orbit around the Sun. Even with the intercalary months the Lunar months slide across a sixty-day wide zone of the year. Does this matter?
It depends what you’re using the calendar for. If you’re planting crops by it then yes it does. How do you solve this problem? The earliest gardening manual we have is Works and Days by Hesiod which dates from very roughly around 700BC. He doesn’t use months, instead he looks for various signs, like the first rising of a star, it’s heliacal rising, in the morning sky. Even this wouldn’t be perfect, because some years have colder winters than others or later Springs, depending on the weather. So he also looked for other signs like birds flying back from migration or the return of snails. What he didn’t use was a calendar because that would have just been a mess.
The Greeks knew it wasn’t that accurate. Herodotus notes:
the Egyptians, they said, were the first men who reckoned by years and made the year consist of twelve divisions of the seasons. They discovered this from the stars (so they said). And their reckoning is, to my mind, a juster one than that of the Greeks; for the Greeks add an intercalary month every other year, so that the seasons agree; but the Egyptians, reckoning thirty days to each of the twelve months, add five days in every year over and above the total, and thus the completed circle of seasons is made to agree with the calendar.
That didn’t matter because the Greeks weren’t using it as an accurate measure of time, they were using it to talk to the Gods.
The Greek months tended to be named after a big festival that happened in them. The festivals were big religious affairs for the Gods and tended to happen roughly around the same time of year, but usually it didn’t matter if they weren’t at exactly the same time as last year. In fact a little unpredictability might even have been a good thing. Religion and festivals were also central to civic identity. While the Greeks worshipped the Olympian Gods they all worshipped their own version of the Olympian gods. The Delphinians revered Apollo Delphinios, while in Eretria they had Apollo Daphnephoros. Taking part in a religious festival was affirming your right to be part of that city. This is not something you would want to encourage in outsiders.
Even with the considerably more accurate Julian calendar of the Romans, it was still religion that was at the heart of the calendar. Days would be marked out as to whether they could be used for some events or not as noted by the Fasti.
It would appear that the last thing that you could use a calendar for is agriculture. Nature doesn’t care if a day is auspicious or not. If it’s going to rain then it will rain and the wise farmer will get his harvest in before a storm ruins it. Calendars only work when people pay attention to them so it would appear that the main function of a calendar is to control people rather than nature.
This is one of the problems in reconstructing prehistoric calendars. Prehistoric calendars would have made perfect sense to people born into and living in the relevant mythology. Unfortunately we have lost the mythology of prehistoric times, so often can only make rough guesses as to what a prehistoric calendar might have been like. The one strong conclusion I would be willing to come to is however it worked it would have been flexible. The people operating the calendars were not stupid and would not have picked and argument with Nature. —–
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