[dredmorbius]

Eviatar Zerubavel's Seven Day Circle is a detailed and complex history of time telling.

It really helps to understand that in a calendar we're trying to measure three distinct (and variable) cycles, none of which fits precisely into the others, and each of which imposes its own rhythms on human life. Attempts to break each from the current 7/12/365 basis have virtually all failed.

The first is the Earth's rotation about its own axis -- different when measured with respect to the stars or the Sun.

The second is that of the Moon about Earth.

The third is of the Earth about the Sun.

We overlay them on each other and pick rough correspondences.

Much of the division has to do with Babylonian time reckoning, based on 360, and its factors: 2 * 2 * 2 * 3 * 3 * 5. From that you find 2, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 45, 72, 90, 180, and 360. A seven-day week doesn't fit this directly but is close (between 6 and 8), and a 30-day month also fits well.

Then you come to realize that all timekeeping, _especially_ that which picks a specific starting point, is arbitrary.

The book also details several attempts to change the system, particularly following the French and Russian revolutions (oh, and the reason for that being the October revolution -- and there's the question of what was the last nation to adopt the Gregorian calendar, and why the output of 'cal 1752' is what it is ... and why even _that_ is arbitrary (it depends on where you're specifying the date).

http://www.powells.com/biblio/61-9780226981659-2

[tjradcliffe]

In New England (and likely elsewhere) you can see gravestones from the sixteen and seventeen hundreds that have two death dates on them, as different parts of the world converted to the Gregorian calendar at different times, and both Gregorian and Julian dates were in use in the area for a while (parts of Europe converted as early as the late 1500's).

[canjobear]

It's not clear that the rotation of the moon has much significance in modern life any more, so maybe the problem can be simplified.

What was the significance of cycles of the moon in the past, anyway? The main thing I can think of is astrology. Can tides be predicted accurately using phases of the moon?

[dredmorbius]

"What was the significance of cycles of the moon in the past?"

Really not my metier, but a few thoughts.

The Moon is highly significant if you're living along a coastline (and most humans do) as the tides are directly related.

In a pretechnological society, the biggest and cheapest source of night-time lighting was moonlight (though you could locally out-shine it with torches, candles, or lanterns). For travel or any sort of nocturnal activity (including ocean navigation), you'd likely take it into consideration.

In arctic cultures, moonlight might be your only light for much of the year, and on snow, full moonlight is amazingly brilliant.

In terms of dividing up the the year, different moons, particularly named moons ("hunters", "harvest", etc.) are significant.

[triangleman]

Month = "Moonth"

Aside from the female menstrual cycle, the gestational cycle is also in line with the moon: A baby is brought to term in 10 moons or 280 days (9 months or so).

You would also have an easy way for disparate peoples to mark time, since in the past there was no such thing as telegraphs or even pony express.

[xorcist]

That's only because we have a weird method for calculating pregnancies, for historical reasons.

A human pregnancy is around 266 days +- 16. The reason for 280 days or 9 months is because that measures the time span since the last menstruation, not since conception.

(I was personally a bit surprised by this when expecting our first child. It's one of those things you apparently know about but still use "9 months" as a bit of a fixed expression.)

[cbd1984]

> Aside from the female menstrual cycle

Birth control pills have a big effect on this now.

> A baby is brought to term in 10 moons or 280 days (9 months or so).

If you can't tell how far along a pregnancy is without reference to the Moon, there's no help for you.

[zhte415]

It is extremely important in agriculture, which much of the world sustained, and sustains, itself on.

[Ma8ee]

How is the moon's phases important in agriculture?

[toyg]

>How is the moon's phases important in agriculture?

traditional agriculture uses the moon to determine what to plant when.

i'm not saying this actually makes a difference (altho it might, considering the moon does influence sea levels and hence how water flows through the system), just that it's what agriculture is traditionally based on.