Calendar Trivia

There is a large collection of stories circulating which are in some way tied to the calendar. This is probably in part because of the aproach of the year 2000 and an overload of "21st century" rhetoric.

Some of this has to do with real (or asserted) problems in the world, such as how computers deal with the year 2000. Others are about items which really make no difference to anyone's lives, such as whether the 21st century starts in 2000 or 2001.

Curiously, the latter group generates more passionate debate.

Sections in this page:

Calendar Systems

Among the nearly useless (outside theological circles) pieces of information bantied about are details of the differences among the calendar systems which have been used. The current calendars are modifications of the Julian Calendar. These modifications have been needed because of errors in the average year length for the Julian. (The astronomical length of the year is 365.24219 days).

These calendars (an their errors) are:

Calendar Year length Error Years for
one day
Julian 365.25 0.00781 128
Gregorian 365.2425 0.00031 3225
Revised Julian 365.24222... 0.0000322... 31034
Lasnerian 365.two-fifty more or less a bunch

[I've had mail from one person stating that the above information is based on a misconception of the year, since I used the mean astronomical year rather than the mean interval between vernal equinoxes. Personally, I can't understand the detail enough to know whether he is right, and his web page explaining it has vanished. But there it is.]

Unlikely Dates

Another interesting group that occasionally comes up are claims that some date combination is more (or less) likely than might be expected.

The two that I've encountered (both in AFU threads) concern:

Both of these rely on the fact that the date distribution under the Gregorian calendar is not uniform, when taken over long timeframes.

The result is that some things are slightly more or less likely than even distribution. Which way it goes is a consequence of the (IMHO) arbitrary alignment of the Gregorian calendar.

Calendar Links

There is a wealth of more detailed calendar information on the web. Here are some of the sites I used while looking for some of the details I'd forgotten:

Back to the shiny objects

Copyright 1997 (etc.), Drew Lawson.
[Last updated: 1 July 2003]