I’d say this question is equivalent to “When did people realise the fundamental incompatibility between lunar and solar calendars?”, and the answer to that question is “Quite early”. The basic problem is that there is a non-integer number of lunar cycles (synodic months) in a solar year. A synodic month has 29.53 days, a solar year 365.24 days, so there’s about 12.37 months in a year (in antiquity the numbers were a bit different owing to the gradually declining rotational speed of the Earth, but the problem remained). We know that the ancient Egyptians tried to fix that by having twelve months in a year followed by “Epagomenes” - days that don’t count as part of any month, to fill up the number of days after twelve months to what is required for a full solar year. Of course that doesn’t quite work out, since the lunar cycle also continues. If you want to be in long-term sync with both the Sun and the Moon, your best bet is therefore to have a complete intercalary month, i.e. a thirteen-month year, every now and then (seven times in 19 years, to be exact). But of course, it’s possible to ditch synchronisation with either the Sun or the Moon entirely, and rely only on the other. Western calendars preferred alignment with the Sun and therefore have only very loose alignment with the Moon; the Islamic calendar chose the opposite way. The Hebrew calendar still maintains alignment with both by means of intercalary months, but pays the price of having unusually long years in those cases. This fundamental dilemma was certainly understood by the ancient Egyptians and Babylonians.
Not to mention the Maya, who had a more complex system.
… and India and the Far East.
This goes off-topic now, but I once read an interesting book about the history of number systems which mentioned that the Mayan fascination for astronomy even carried into their mathematics, with the unfortunate result of rendering their number system very cumbersome. It was a base-20 system, but an irregularity was that the second-lowest digit position, and that one alone, was base-18. That gave you a set of 360, corresponding almost to the number of days in a year, but it introduced a rupture in the number system that made it largely unworkable.
Obviously that system was not unworkable, since the Maya did complex and accurate astronomical calculations with it, and built many large and imposing structures that needed precise calculations.
It seems that the author was ignorant of the methods of working with the system, so he has made a sweeping statement, probably based on cultural and modern-day bias.
I’ve even heard people say that Roman numerals were unworkable for calculations, when in fact they were very practical.
To wrap this up, the book is “The Universal History of Computing” by Georges Ifrah (an English translation from the French original titled “Histoire universelle des chiffres”), and the passage is:
However, as a result of its forced conformity to the peculiarities of the Mayan calendar, this number-system exhibited an irregular use of the base 20 beyond the third digit position which robbed it, along with its zero, of practical operational value
As I said, he is clearly and obviously wrong.
He was ignorant of the fact that the Maya used a consistent base-20 positional number system for most calculations.
The modified system with the third place value representing 18, and a completely different set of number symbols, was used only by priests for certain ritual and calendar calculations.
The birthdate of everyone I know from East Africa–well, Somalia, at least–is January 1st. That’s not really the day they were born, obviously, but just the date the government puts down when they get a passport. Most parents in Somalia (or maybe just the ones from rural areas) don’t record their children’s date of birth. But they do know how many years old they are.
Anyway, if you ever run into someone from Somalia on New Year’s Day, be sure to wish them “happy birthday.”
note too - things like Easter happen as “the first Sunday after the first full moon after the spring equinox”. When you base “day of the year” on the phases of the moon and the resultant asynchronicity of moon and solar cycle, then marking “this is the exact day of the year you were born” becomes a lot trickier to nail down, or less meaningful. it’s only when the particular month counts from the same number of days every year from, say, the solstice - that we can say the “10th of Thermidor” represents the same number of days into the year every year. (And even then, leap years mess things up)
I assume it actually becomes more relevant to mark exact days of the year when commerce gets involved, which is much later in human social evolution. Events where things are paid at regular intervals through the year (i.e. 12 times a year for rent) probably are less tolerant of complex calendars. If we have a 5-day “special” time to complete a 360-day year, how much rent is due for that time?
That’s a bit ironic coming from a Frenchman, given that the French language still retains evidence of an ancient base-20 counting system in the language.
If it’s only five days at the end of the year I expect it’s no more disruptive than our current system where some months have 30 days, some 31, and one month has either 28 or 29. I pay the same rent every month - not more when there are 31 days or less when it’s 28 or 29. A 360+5 day calendar society would work it out.
You know, we have a similar phenomena in some North American cities called things like Manhattanhenge, Chicagohenge, Torontohenge, MIThenge… But it has to do with a passion for laying out strict grid systems for city streets aligned with specific directions, not the particular days of the year this happens.
This won’t contribute anything scientific to the discussion, but there’s a humorous story in the Arabian Nights about a man called Abu Hasan who, after having eaten a lot of good food at his wedding feast, farted on standing up from his seat. Although his friends pretended not to notice, he was so ashamed that instead of going to bed his bride, he left home and got on a ship bound for India. He got a position with a rajah and for a long time remained in self-imposed exile. At last, after 10 years, Abu Hasan decided to go back to his native land. On coming to Baghdad, he didn’t go directly into town but spent days wandering around the hills, hoping to learn from someone about whether he still had a good reputation. On coming to a shepherd’s hut one night, he overheard this conversation between a mother and a child:
“Mother, when was I born?”
“Oh, that’s easy, my dear,” the mother laughed, “You were born in the year that Abu Hasan farted!”
With this, his all his hopes died. He left the land and was never seen again.
Depends.
I imagine in olden days, the majority of peoples’ income was for food. An extra 5 days would require a certain compense, or someone would have to do 35 days on a budget of food for 30 days. More likely people would pay by the day. I assume that’s as you point out, a more reasonable way to adjust. IIRC, before Julius, they just tossed in a few feast days whenever the official calendar got too obviously out of sync with the stars.
IIRC, there was a certain amount of unrest when the English world adopted the Gregorian calendar and dropped those 11 days to get in sync. Some landlords expected a full month’s rent regardless, but workers were paid by the day. .
This is one of the instances where the Gregorian calendar reform was remarkably well prepared and thought through. In Inter gravissimas, the 1582 papal bull that introduced the calendar, Gregory XIII stipulates:
But in order that nobody suffers prejudice by this our subtraction of ten days, in connection with any annual or monthly payments, the judges in any controversies that may arise over this, shall by reason of the said subtraction add ten days to the due date for any such payment.
(Source: Inter gravissimas - Wikisource, the free online library)
Of course, English Protestants, when adopting the calendar, wouldn’t regard a a papal bull from two centuries before as a source of law binding on them. But it shows that such problems had been seen and considered in advance.
I looked it up, seems the Act of Parliament that introduced the Gregorian calendar in Britain (British Calendar Act of 1751 - Wikisource, the free online library) also foresaw the issue and included extensive provisions about the impact of the reform on due dates for payments or delivery of goods. The basic rule was that the due date would remain on the same natural date as before, i.e. it would be postponed by eleven days under the reformed calendar to make up for the omission of those eleven days.
Which makes me wonder whether there are still any extant obligations that are still affected by this provision. Are there any pre-1751 contracts that originally stipulated periodical end-of-month payments which now (and to this day) take place on the 11th of the subsequent month by virtue of this act?
The UK tax year still runs until 5 April. Before the calendar change, it ran until 25 March.
The date of 25 March was due to the medieval ‘quarter days’.
This also has a bearing on the discussion about rents. Medieval rents were due every 3 months, approximately, not every month.
There were four ‘quarter days’ that corresponded roughly to the equinoxes and solstices:
- Lady Day (Mar 25)
- Midsummer Day (Jun 24)
- Michaelmas (Sep 29)
- Christmas (Dec 25)
These were the days when rents and payments were due, and contracts normally ran between quarter days. Land tenure was always for a year, from Lady Day to Lady Day, for agricultural reasons.
That’s very interesting, thanks. I can see why an agricultural society would have land rent from spring to spring (so that the same tenant who sowed crops also gets to keep the harvest), but it’s fascinating to see that this, in combination with the eleven-day omission of 1751, still defines the British fiscal year.
I agree with all of this. But how important was a birthday to them? My next door neighbor seems to care a great deal about some Kardashian (I have no idea which one). I’m guessing if she was working in the field for 10 hours a day, was hungry, and didn’t know if she’d have enough food saved this winter that should wouldn’t give a rat’s ass about what ever Kardashian was doing what.
I don’t think they knew because one, it was harder to track, and it wasn’t worth the time and effort in their markedly more difficult lives.
In prehistory, we have no real way of knowing. I think “not very” is a perfectly reasonable guess.
I’m only pointing out that humans had the tools to measure birthdays with reasonable certainty long, long before written language emerged. If they cared to remember, they could have.
I agree. Considering how vague birthdays can be in relatively recent times, I’m sure in a lot of societies, time keeping in terms of a calendar was left to the priests or scribes, and everyone else just did their thing without knowing or caring what the year was. I mean, if you were a grain farmer in southern Gaul in the year 221, did it matter if you knew it was 221? Did that guy care? Probably not. Same for some French farmer in Provence in 1430. He might be aware of the year, or that numbered years existed, but there wasn’t much utility in them for him.
Meanwhile, I’m sure that the priestly class in Stonhenge-era Britain probably could tell the passage of a year with great accuracy. Same for a lot of other pre-literate societies.
I mean, i can tell you my birthday with great accuracy. But i have three of them. I have the day i was born in the secular calendar, the day i was born in the Jewish calendar, and the day i was born for purposes of family celebrations: i was born on Thanksgiving, and often celebrate my birthday on Thanksgiving.
The whole concept of birthdays is a bit vague.