Much ink has been spilt over computers' Y2K problem, but very little attention has been paid to the underlying flaws in the solar calendar itself. As Stephen Jay Gould points out in his charming Questioning the Millennium--an indispensable rationalist's guide to millennarian claptrap--"We have been oversold on nature's mathematical regularity." The problem is that there really aren't 365 days in a year. There aren't even 365 and one-quarter days (though most everybody assumes that the Julian calendar's leap-year fix straightened everything out). There are 365 days, five hours, 48 minutes, and 45.96768 or so seconds.
The Julian calendar's accumulated surplus of minutes had by the 16th century moved the vernal equinox up by 10 days, from March 21 to March 11, thereby screwing up astronomical calculations used to determine when Easter should fall. Pope Gregory XIII was not amused. So, after consulting with a committee of experts, he proclaimed on Feb. 24, 1582, that 10 days in October--the fifth through the fourteenth--would be eliminated! Sure enough, when October rolled around, Oct. 4 was followed by Oct. 15.
Britain, disdaining popery, didn't adopt the Gregorian fix until 1752, by which time it had to eliminate 11 days--Sept. 3-13--to get the equinoxes right. The Russians didn't make the fix until the Bolsheviks took over in 1918, which may explain why nothing in that country has worked ever since. According to Gould, the belated changeovers in Britain and Russia account for amusing calendrical oddities such as George Washington's birthday sometimes being given as Feb. 11 (Julian calendar) and sometimes as Feb. 22 (Gregorian), and why the Soviets always used to celebrate the anniversary of the October revolution in November.
Will human civilization have to knock another 10 or 11 days off the calendar anytime soon? No, because Pope Gregory, in addition to fixing the accumulated error in the solar calendar, took two steps to prevent similar accumulations in the future. Step One was to eliminate leap years whenever the century turns. (Nobody knows about this because only perhaps the odd centenarian remembers failing to show up for a scheduled appointment on March 1, 1900.) Step Two was to reinstate leap years in century-turning years divisible by 400. As a result, next year will be a leap year, just like most people, out of sheer ignorance, already expect it to be.
After all Pope Gregory's intricate twiddling of the dials, the Gregorian calendar remains an exasperating 25.96 seconds out of synch with the sun's comings and goings. That's going to put the calendar one full day off by the year 4382. Hence truly forward-looking people (Al Gore: Are you listening?) should worry not about Y2K, but about Y4382, when we will have to alter our calendars by one day. This will surely cause all the computers on planet Earth to explode.