Leap Day 4000

Factual Questions
1

Cecil –
EMERGENCY LETTER!
If you have not already written in advance all your columns up to Leap Day 2000, please address this important issue before that fateful day!

    Everyone knows that all years divisible by four are leap years. And by now, anyone paying attention to the media know-it-alls has learned of the exceptions: that years ending in --00 are usually NOT leap years, unless the --00 year is divisible by 400 in which case it IS again a leap year. So that Leap Day 2000 is an incredibly rare event that crops up only once every 400 years -- February 29 occurring on the first year of a century.
    Here's my question: The earth takes approximately 365.2422 days to go around the sun. To accomodate for this annoying fractional day, we have devised a series of exceptions (leap day every four years), exceptions to the exceptions (no leap day in -00 years), and exceptions to the exceptions to the exceptions (unless that --00 year is divisible by 400). When you add up all the fractions and convert to decimal, you find that ON AVERAGE over a span of 400 years the length of a year according to our calendar is 365.2425 days -- which is pretty close to reality. But not close enough for some people. I have read in more than one musty treatise of a proposal to make the calendar even more accurate by declaring all years divisible by 4000 (i.e. 4000 A.D., 8000 A.D., etc.) NON-leap years, even though they "ought" to be leap years according to the "leap if its divisible by 400" exception, which we are observing right now in 2000 AD.
    This ultimate refinement of the calendar would make the length of an average year over a span of 4000 years to be 365.24225 days (correct me if I added up my fractions wrong), a level of accuracy so precise it that will keep the calendar pretty much on track with the natural seasons until the earth starts slowing down in its orbit or the sun supernovas.
    This "no leap year in 4000 A.D." proposal was bandied about in the '30s and '40s, but the last reference to it I can find is from 1945. What ever became of it? Was it officially adopted, and is now an acknowledged but rarely discussed part of our calendar system? Or was it abandoned and forgotten? Or has the system of "leap seconds" we hear about occasionally taken the place of the 4000 A.D. rule?
    Cecil, help! We're already halfway to 4000 A.D. and we've haven't even resolved this life-threatening issue! Sure, Y2K was a blowout, and Y10K is too far off to worry about. But Y4K -- now THERE's a disaster waiting to happen. I've started stockpiling flamethrowers and granola bars already --JUST IN CASE.
                                                                                                    -- Tuffy
                                                                                                            Berkeley, CA
2

You’re just crying wolf! Look at history.
-Y2K, -Y1K, OK, and Y1K are all divisible by 0 and all passed without a hitch. Why would Y3K and Y4K be any different?

3

This is already answered in Cecil’s Mailbag:
Why do we have leap years?

4

Cecil to the contrary, the best information I can obtain at present is that the 4000-year rule has never been made official. In fact, it’s really too slow. For the system to work, each new adjustment has to overcompensate, whereas the proposed 4000-year undercompensates, and would eventually result in having to leave out two leap years around 20,000. The right extension to the system would have been to omit all leap years divisible by 2000 and then make yet a further exception to that rule.

However, what with leap seconds and the gradual slowing of the Earth’s rotation, I suspect that the wisest choice is simply to keep the present rule and omit an occasional leap year every few thousand years on an as-needed basis.

John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams

5

I, personally, would be happy if the mankind was around long enough for this to make any difference. Otherwise, really, folks, calendars are all a matter of convenience anyway, so who CARES? :slight_smile:

6

John – The Mailbag article was not written by Cecil, but was taken from the Encyclopedia Britannica (among other sources.) You are correct, of course, that sufficient unto the day is the evil thereupon.

7

The Encyclopedia Britannica article mentioned above is all very well and nice, but it’s the same article that has appeared there since the '40s and does not seem to have been updated since then. As John pointed out, there’s seems to be no evidence that the 4,000-year rule was ever officially adopted. Updated question: Was the 4,000-year rule OFFICIALLY adopted (not just referred to as wishful thinking in an encyclopedia article); and BY WHOM was it officially adopted? That is, who is in charge of the Gregorian Calendar these days? The Pope? Greenwich Observatory? The old “Cecil’s Mailbag” article doesn’t really clear things up completely.

8

I think the current plan (not yet widely disseminated, so don’t spread it around) is to skim asteroids and/or comets by the Earth to raise the Earth’s orbit until the period is exactly 365.2425 days. Problem solved. It also helps with the greenhouse effect problem, as an added bonus. It’ll take a while, but we’ve got some time. With the rapid advance of technology, actual work should start within only one or two hundred years.

I think they’ll also fix the problem with the precession of the Earth’s poles at the same time, but don’t quote me on that.

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Hmmm… I’m in GQ, not MPSIMS, so I better put a smily in here somewhere. :slight_smile:

It is too clear, and so it is hard to see.

9

I was under the impression that the Britannica was completely rewritten for the 15th edition (1974 or so).

John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams