Retorts

Celebrating the Millennium

I read with interest Bill Keir's article on "When Should We Celebrate the Millennium" [Viewpoint, May]. This question is easy to answer, but it would appear to be difficult to convince some people.

To understand the dispute we need to look at the work of the monk Dionysius Exiguus or Denys the Little in the sixth century AD. He was making a table of the dates of Easter and decided to count the years since the birth of Christ, instead of the beginning of the reign of the Roman emperor Diocletian, which was the convention at the time. Hence the year 248 Anno Diocletiani became the year 532 Anni Domini Nostri Jesu Christi.

Denys made two unfortunate mistakes. Firstly and understandable, as the number zero had yet to be discovered in the West, he called the first year of his era year one, assuming that Christ was born at the end of the preceding year. That was his second mistake, for it is now thought that Christ was probably born between 6BC and 4BC (when Herod died). It is interesting to note that it was the Venerable Bede who invented, in the eighth century, the concept of years BC and it was not until the eleventh century that the usage of AD and BC became generally accepted.

Therefore Denys the Little's first mistake when counting the years meant it is the end of the year, not the beginning, that marks the interval of years that has elapsed, indicated by the name of the year. This meant that only on December 31 of year one had an interval of one ear elapsed, therefore the first century ended in year 100 on December 31. Consequently the Twentieth Century and the Second Millennium will end on the year 2000 on December 31. For it to end in 1999 on December 31, one of the previous centuries would have only had 99 years! Another way of explaining this is to think of a cricketer scoring a century. The century is not achieved until the 100th run has been completed. It is not the same as birthdays as you become a centenarian at the end of your 99th year because you are zero years for the first twelve months of your life.

The calendar that is used mainly in the Western World is called the Gregorian calendar after its introduction by Pope Gregory XIII in Rome in 1582. Christopher Clavius advised the Pope to introduce the new calendar to sort out various problems with the Julian calendar regarding the date of Easter and leap years. It was decreed in 1582 that for a leap year its number had to be divisible by four, but in a centenary year (note the word "centenary", one that ends in two noughts) its number had be be divisible by 400. So by definition this forever excludes a year ending in "99" being divisible by 400 and therefore excludes forever such a year from being a centenary year (the end of a century).

This will not be the first Century that this controversy has arisen. It would appear that it has happened over the last few centuries. The Times of London obviously had numerous letters towards the end of 1799 for the editors to make these comments in the letters column of the 1799 December 26 edition:-

"We have uniformly rejected all letters and declined all discussion upon the question of when the present century ends, as it is one of the most absurd that can engage the public attention, and we are astonished to find it has been the subject of so much dispute, since it appears perfectly plain. The present century will not terminate till January 1, 1801, unless it can be made out that 99 are 100 ... It is a silly, childish discussion, and only exposes the want of brains of those who maintain a contrary opinion to that we have stated".

It would appear the only reason that is put forward for the beginning of the new Century/Millennium beginning at the start of year 2000, is that it is "what people think". People thought that the Earth was flat and that the Moon was made of cheese; it did not make them right, it just meant they were ignorant of the facts.

Brian Carter, Senior Astronomer, Carter Observatory, Wellington