Re: Why not 13 months? (Was La Systeme Metrique)

Stephen Souter (
25 Jul 1995 03:17:52 GMT

In article <>, (Isolde) wrote:

> I'm no astrologer or astronomer, but I like the 13 month calendar made of
> 28-day months--moon-ly months, mind you, not political ones! The
> arbitrary and political basis for our monthly system has no business in
> the reckoning the natural year!!!

"No business in reckoning the natural year"?

One cannot choose but wonder how the human race is going to cope once it
starts living on worlds where the "natural year" happens to be something
other than 365 days!

Human calendars are for human convenience. They have been devised because
it is the *natural* year which is arbitrary. Human calendars only seem
arbitrary because the "natural year", however you define it, is not only
not a whole number but not even a convenient whole number.

A year made up of thirteen 28-day months (=364 days) does indeed *almost*
fit the natural year.

The chief problem is that 13 happens to be a prime number. This makes it
mathematically impossible to subdivide a year in any satisfactory fashion.
You cannot even divide such a year into the customary four seasons and
hope to come out with the same number of whole months in each season.

By contrast, a 12-month year can be easily divided into halves
(six-monthly periods), quarters (3-monthly), thirds (4-monthly), and
sixths (bimonthly) of more or less equal size.

Stephen Souter