My question is really about calendars, I suppose. Days, months, and years obviously correspond to celestial events and therefore seem to be natural divisions of time. But how did we end up with a seven day week? I know that there are Biblical foundations for this, but not everyone reads the same religious texts. How is it that the world seems to use the same days of the week (translated into the appropriate language) and agrees on the same number (i.e. 1995 or 2005) for the year. Again, this number has a religious basis, yet those with differing religious histories seem to be able to agree on the date.
So, does in fact the entire world agree on a single calendar? How do two different cultures agree on the date? Do we sometimes convert dates to locally understood conventions?
(And a related question: How come the US seems to be the only nation to use a mm/dd/yyyy date format while the rest of the world does very well with the more logical dd/mm/yyyy format?)
I don’t think there’s anything inherently more logical about dd/mm/yy than mm/dd/yy. dd/mm/yy puts the numbers in gradually ascending order, least significant digits on the left, greatest on the right. This isn’t necessarily logical because it’s the opposite of how our counting system reads (most significant digits on the left, least on the right). yy/mm/dd would be far more logical by that definition.
dd/mm/yy would be a system very advantageous for short-term planning where the most important information (how many days from now?) is expressed first. That’s not too different from how the Romans used to do it.
The mm/dd/yy system could be considered logical and useful for everyday conversations, where for the purpose of long-term planning a human might wish to first convey a generality (the season, the month) before assigning it fine detail. The French language works in this way, assigning nouns before adjectives, and yet mm/dd/yy is considered illogical? I don’t see it’s particularly more or less logical than conventions humans adhere to.
Why would saying “the third of May” be any more logical than saying “May the third”? Why do we not use the metric system? [sup]Those damn Brits probably had something to do with one calendar being used.[/sup]
How today’s calendar came about can’t really be explained in a paragraph. It was a long and involved process, concerning dozens of people and cultures over thousands of years.
Duncan is mostly interested in measuring the length of a year and how people reconciled the variation between the lunar calendar and the solar calendar, which goes to the OPs question on how everybody (mostly) today agrees on a particular date in a particular dating system. The year is not at all a “natural” division, no matter what we think today.
And the why of the seven day week he ascribes to Constantine, who changed the complicated and bizarre Roman calendar to a seven-day week when he embraced Christianity.
And this is at least partly to make machine sorting (or collation) as trivial as possible. In that format, a naïve alphanumeric collation makes things come out in chronological order, as opposed to the mess that results from MM-DD-YYYY or DD-MM-YYYY.
No, through trade, and yes.
The Japanese, for example, who use the Western (Gregorian) calendar for most things and all international trade, still maintain their own traditional system of dating from the beginning of the current Emperor’s reign. The Indians (from the Subcontinent) have their own civil calendar (established 1957) that is similar to the Gregorian, except their current year is 1927. The Muslims, Jews, and Persians all have their own traditional calendars as well, with wildly divergent ideas about what year it is now (the Jewish calendar, which ostensibly dates from the beginning of the Universe, puts today’s date at 5765 Tammuz 28, whereas the Muslim calendar, which dates from Mohammed’s flight from Mecca to Medina, puts us at 1426 Jumada t-Tania 28).
[sup]Those damn Brits probably had something to do with one calendar being used.[/sup]