Why it's such a rare occasion

Today is the most unique day on the calendar. February 29 has occurred only 103 times in history, and only 14 of those occasions have been a Sunday. That makes today pretty unusual.

But while many much more "common" days – like Christmas and New Year – cause a global frenzy, Sunday, February 29, 2004, for all its rarity, will pass virtually unnoticed.

To the best of my knowledge, it will be celebrated only as "World Hash Day", like every other February 29, by that rag tag army of folk who call themselves "The Hash House Harriers". 

It's a sort of club, with no formal membership or subscription. The "Hash" in hundreds of cities throughout the world (including Nairobi and Mombasa) simply passes the word around that there will be a fun run, a sort of joggers mix-in, on a regular day of each week, in one of the suburbs.

If you want to run, you simply turn up at the appointed rendezvous, say hello, and off you go. Each week's course is set by someone with serious lungs and leg muscles, who runs ahead leaving a trail (of little scraps of loo paper or little piles of posho). 

No one knows where he's gone, so the Hashers spread out in all directions looking for the first trail clue. When someone finds it, he or she shouts "on, on", or something, and everyone follows the sound – and the trail. The best runners tend to do all the scouting and finding, and the rest cover a much smaller distance at much lower speed while waiting for the next shout and then taking a short-cut. The net result is that a course of eight to 10 km takes nearly two hours, and almost everybody, athlete and arthritic alike, finishes at about the same time. All then shout "Jolly Hockeysticks", or something, agree where they'll meet the following week, and then go home.

You will have guessed that such a pastime must have British origins (the world's most prolific inventors of peerlessly eccentric games), but like cricket and football before it, the "Hash" now has a worldwide following. Today they'll all be saying hello, on-on, and jolly hockeysticks in unison – as they scale the Mt Longot.

And that is perhaps appropriate, for February 29 is quintessentially eccentric; always has been and always will be. It's completely crazy. It's also incredibly important. 

If February 29 was not necessary, we would not exist. Let me explain: 

The first precise measure of time man discovered was the Day. The time it took for the earth to rotate once on its own axis. This is exact, consistent, and it relates to our natural physical environment. No problem with the Day. 

And no problem with how we divide up that Day into smaller parts; the concepts of hours, minutes and seconds are pure human invention (based on equally arbitrary degrees of angle) and all we have to do is agree what they are and have a way of defining them. It's just a pity we didn't choose 10 hours, each containing 10 minutes, each divided into 100 seconds.

No problem, either, if we just invented terms and definitions for collections of Days – ideally, 10 days = 1 week; 10 weeks = one month; 10 months = one year. Everything would then be related, precisely, to the natural, physical, real, Day. Metrically. 

Unfortunately, in our search for bigger time blocks than the Day, we discovered the Moon and the Sun before we invented metric maths.

We worked out how long it took for the Moon to go round the Earth once, and how long it took the Earth to go round the Sun.

Had there been an exact number of Days in the Moon's orbit, and an exact number of Days and/or lunar cycles in our regular circuit of the Sun, we could have had a very sensible calendar – not metric, but manageable.

Unfortunately there are 27.3 days in a moon cycle, and it takes the Earth 365.2422 days to orbit the Sun. Any attempt to have all three units – Days, Moons and Suns – in the same calendar was arithmetically doomed. Yet that is what man did, continued to do, and still does.

Julius Caesar and his astronomer buddy Sosigenes tried to repair the cumulative damage by announcing one year (the one we call 46 BC) would have 445 days and that every third year thereafter would be a Leap Year. Thus began the Julian Calendar. 

Interestingly, 46 BC became known as "the year of confusion", and the Leap Year frequency meant calendars were gaining on real solar time by 2 hours and 11 minutes. With a fellow whose name sounded like Sausage Knees in charge of the abacus, the mad maths is hardly surprising.

In 8 BC, Emperor Augustus cut the error to 11 minutes by revising the Leap frequency to every fourth year, but by the 16th Century, even that little quirk had accumulated to an error of 11 days.

So in 1582, Pope Gregory XIII decreed that October 4 should be immediately followed by October 15, and with a nifty bit of foresight he built in a future correction by saying that the years 1700, 1800 and 1900 (the century years not divisible by 400) would not be Leap Years – cutting the error to about 4 minutes. The fact this idea came from Rome caused riots in the Protestant world who wanted their 11 days back, but quite quickly the Gregorian Calendar became, and remains, the one we hang on the wall.

We? Well, Christendom and commerce. Muslims' years have between 354 and 355 days each and their Year Dot is approximately 0.622 Millennia later than Greg's; the Jewish Calendar varies from 353 to 385 days per year; the Chinese Calendar (banned in China since 1930 but still used elsewhere in SE Asia) runs on a 60-year cycle.

And those are the variants even among linear time cultures (Judaism, Christianity, Islam) which posit that things have definite beginnings and ends, that time progresses from A-Z and therefore significant historical moments occur on the way towards an ultimate purpose; but there are big chunks of humanity who belong to cyclical time cultures – Hindus, Buddhists, Sikhs – whose perspective of time is an unbeginning and unending chain, a repetitive cycle, a constant reiteration of eternal truths, with no unique events in time. 

Personally, I can grasp the "Day" bit – the time it takes the world to rotate once. It's the same, every time, all the time.

I can also grasp the "Year" bit – the time it takes the world to orbit the sun once. It's the same, every time, all the time, I think. 

It's also not too difficult to understand the "Moon" bit – the time it takes the moon to orbit the earth once. It's the same every time, all the time.

But three things stagger the imagination. First, how old Sausage Knees managed to work all that out so exactly 2,050 years ago! And second, what possessed anyone of such obviously remarkable intelligence to try to put the day and the year on the same calendar, when they knew the two things would never synchronise; and then why did they divide that impossible calendar into unequal fractions called months, which did not synchronise with the moon and had an irregular number of days in each one. And third, why, two millennia later, when we have progressed science to such a degree we can measure femtoseconds, do we persist with this diabolical dogs' dinner of a date system.

Femtoseconds? Yes. You know, one millionth of one billionth of one second. 

The actual time used to be a really tough call between the sun dials of 3500 BC until the first mechanical clocks of the 14th Century that were driven by falling weights; or the first watches of the 16th Century that used coil springs; or the Regulator Clocks of the 17th Century which used pendulums; the Marine Chronometers of the 18th Century that didn't have to be upright; the Quartz Clock of 1929; the highest-tech digital clocks of today that are accurate to within – 1 second every 10 years.

We can now do better than that . . . with the atomic clock, which is accurate to within 1 second every 1.7 million years because it can count the number of periods of radiation (vibrations) of an atom of Caesium 133 – the answer is 9,192,631,770 times per second. That means we can have femtoseconds – a millionth of a billionth of a second. 

To put that in perspective for you; in one second, a pulse of light can travel almost to the moon. In 100 femtoseconds, it travels the thickness of a human hair. We can measure one femtosecond. 

What, pray tell, is a species with a brain large enough to manage that doing with a thing called February that sometimes has 28 days (which is wrong) and sometimes has 29 days (which is intended to put it right, but doesn't)?

It isn't nature that has messed up things here. We should be very grateful that year is not precisely divisible by an exact number of days. For it to be so would require the earth to be either a bit nearer or a bit further from the sun, so its orbit was very slightly shorter (exactly 365 days) or slightly longer (366 days).

But, as any physicist or astronomer or meteorologist would tell you, that tiny change would have completely altered the evolution of our planet. Human beings, for example, probably would not exist.

So anybody out there who is pleased and proud to be a human being has cause to give thanks for the "February 29th" syndrome. In a way, it helps make us what we are.