18

According to “The Accidental Superpower” by Peter Zeihan:

“The mind-set of eternal stability was so deeply entrenched that when ancient Egyptian scholars discovered that they had failed to account for the extra day in leap years, instead of adjusting their calendars they decided it would be less disruptive to wait until their calendar—too short by 0.25 days annually—simply cycled all the way around again, a process that took 1,461 years. When that day arrived, the Egyptian leadership declined to make the adjustment, since from their point of view the inaccurate calendar had triggered no deleterious events in the past millennia and a half. It wasn’t until the Greeks occupied Egypt that they forced the adoption of an accurate calendar.”

As far as I can tell this is exact story is not substantiated by historical records. But do we have any clue as to why the Egyptians didn’t introduce the leap year concept (or some other method for correcting for the extra 1/4 of a day each year) until very late into their civilization?

Steve Bird
  • 19,763
  • 11
  • 93
  • 99
JonathanReez
  • 4,291
  • 32
  • 50
  • If you’re talking about the Decree of Canopus for the calendar reform, it was not even followed, and really, it wasn’t until Augustus that Egypt had and used an intercalary calendar. – Pierre Paquette Jan 27 '24 at 23:13

1 Answers1

41

Prediction wasn't Required

The main reason to link the solar calendar with the secular calendar is to predict food production conditions.

When is the salmon run? When is the first/last frost?

If you predict the frosts wrong, you will lose your crop. If you predict the salmon run wrong, you might arrive too early and exhaust local resources, or too late, and miss part of the salmon harvest.

In contrast, ancient Egyptian agriculture didn't require this type of prediction.

Ancient Egyptians waited until the annual floodwaters receded, and then planted. They could just observe the flooding, and see that it was complete - no farmer's almanac required.

Frosts were likewise not an issue given the local climate.

Note that over a ~60 year lifetime, the lack of a leap day shifts the calendar by about 2 weeks, so if June was mid-summer as a child, it's still summer at the end of your life.

codeMonkey
  • 1,021
  • 7
  • 10
  • 1
    Precise calendaring is also useful for astronomy. Did Ancient Egyptians not practice it? – SPavel Jan 25 '24 at 18:56
  • 27
    @SPavel - I think its the other way around - astronomy was primarily useful because it helped make a more accurate calendar (via tracking constellations against equinox / solstice timing). People died if you screwed up the timing on the first frost, whereas accurately predicting when Venus was at the horizon was... less important. – codeMonkey Jan 25 '24 at 19:31
  • 5
    An inaccurate calendar is only a problem when you keep the same calendrical rules in effect for a very long period of time. Like ~1600 years for the Julian calendar before Pope Gregory reformed it. Or the similar length of time that the Hebrew calendar has been fixed. In the ancient world, the people in charge just weren't thinking that long-term, so they'd either just live with the calendar drift, or make ad hoc adjustments to keep the calendar in sync with the solar year. – dan04 Jan 25 '24 at 22:33
  • @codeMonkey In a lot of ancient cultures astronomy was also considered useful because the movement of celestial bodies could tell us things about the gods. – SPavel Jan 26 '24 at 00:32
  • @dan04 - Hebrew calendar originated with the Babylonian calendar. The Babylonians forced name changes for the lunar months. The lunar calendars were often up dated to keep them in sync with the seasons. – rcgldr Jan 26 '24 at 01:41
  • 3
    @SPavel : that's right, but for religious purposes astronomy didn't really need an ultra-accurate calendar, the margins for interpretation were beyond a 0.25 per 365 precision range anyway. – Evargalo Jan 26 '24 at 10:36
  • For the calculation of planetary positions the Egyptian calendar is better than any solar calendar because you do not have to worry about leap years. Ptolemy still used the Egyptian calendar rather than the then usual Julian year. – fdb Jan 26 '24 at 11:54
  • @SPavel - Sure, astronomy was culturally important in ancient time. But the periodic nature of comets wouldn't be understood for another 3000 years, so the only things that could be predicted by ancient Egyptians were the constellations and Mercury, Venus, Mars, Jupiter and Saturn. The former is 1 for 1 linked to the solar calendar and equinox / solstice timing. So the only thing being tracked over a longer-than-1-year cycle was the position of the five naked eye visible planets, and I think its understandable that they didn't change their whole calendar system to make tracking them simpler. – codeMonkey Jan 26 '24 at 14:28
  • 6
    @rcgldr: Yeah, before the fixed 19-year cycle was introduced, the Sanhedrin would have to evaluate the late-winter weather conditions, and add a leap month if necessary so that Passover wouldn't start before the prerequisite barley harvest. The Romans had a similar system of having pontiffs declare as-needed leap months, but in practice, the calendar was politically manipulated to hasten or postpone elections, and so had drifted 80 days by the time Julius Caesar decided to replace the highly-inaccurate lunisolar calendar with a solar one. – dan04 Jan 26 '24 at 14:53
  • 1
    The first frost doesn't come on a specific day or even week of the year, why do you need an accurate calendar for that? I suspect calendars were mainly used by government and religious institutions, not farmers and ranchers. – Barmar Jan 27 '24 at 16:01
  • @SPavel: Egyptian astronomy was very basic, at least until the Greeks and Romans. – Pierre Paquette Jan 27 '24 at 23:14
  • 1
    @dan04 Even the Julian calendar included leap days to keep the year in sync with the solar year; it just did so slightly too often. And that reform simply replaced an earlier system that inserted an entire month between February and March as needed. – chepner Jan 27 '24 at 23:33
  • @Barmar - Me: "Grandpa, what's the earliest frost you've ever seen?" -- Grandpa: "Ah, back it '86 it frosted on October 15th!" -- Me: "Cool, as long as the harvest is in by 15 Oct, it won't be ruined by frost." This conv is less accurate / requires more math if the calendar lacks leap days. – codeMonkey Jan 28 '24 at 17:45
  • @codeMonkey I think it's more likely to be "N days after the equinox." -- they'll use seasonal phenomena as their timeline, not a calendar. – Barmar Jan 28 '24 at 19:37
  • @Barmar - "they'll use seasonal phenomena is their timeline" -- that's a calendar! You've just created a solar calendar. But generally, people find it inconvenient to reference dates like "76 days after the Summer Solstice" which leads to the use of divisions, often called months. The problem is, the number of days between Solstice and Equinox is not a whole number, so if you create months with defined numbers of days, the secular calendar will drift from the solar one unless you add leap days from time to time. The drift didn't bother the Egyptians, but it did bother some other cultures! ;-) – codeMonkey Jan 29 '24 at 17:15
  • @codeMonkey I maintain that if the calendar was inaccurate, people wouldn't use it for anything that requires accuracy, they'll fall back on seasonal phenoma that they can observe. – Barmar Jan 29 '24 at 17:19