Naturalist's Almanac

At midnight on December 31, 2000, the U.S. Naval Observatory will drop their time ball to celebrate the beginning of the new millennium. Most people did their celebrating last year when 1999 gave way to 2000, but astronomers and other purists have been holding out for 2001.

Technically, the first year of the third millennium is 2001. That’s because the first year of the first millennium was 1, making the first year of the second millennium 1001, and the first year of the third millennium 2001.

If we wanted our decades, centuries, and millennia to begin with zeros, our first millennium would have had to begin with a zero. But that was impossible because the concept of zero was still evolving among the Hindus in India when the anno Domini, or A.D., system of counting years was invented by a Christian monk in Europe.

In the year people of the time knew as 241 because it had been 241 years since the Roman Emperor Diocletian began his reign, Christians were faced with the fact that their existing cycle of Easter dates would run out in the year 247. Because Christians would be needing new Easter dates to organize their church calendars, a scholarly monk named Dionysius set himself to calculating a new cycle.

He had no trouble using existing formulas to calculate future Easters, but while he was at it, he decided he’d also like to track Easters all the way back to the year Christ was born. His computations took him back exactly 532 years. So in addition to establishing the future dates for Easter, Dionysius also decided to propose a new way for Christians to reckon time.

Christian time would henceforth be counted from the year of Christ’s birth rather than from the beginning of Diocletian’s reign. Dionysius’s new Easter dates would belong to years that would be known as anni Domini nostri Jesu Christi — years of our Lord Jesus Christ — and his first new Easter would occur not in Diocletian year 248 but in anno Domini (A.D.) 532.

If Dionysius had had the Hindus’ zero to work with, maybe he would have counted the years of Christ’s life the way we now count children’s birthdays. The year Christ was born, which marked the beginning of the Christians’ first millennium, would have belonged to the year zero, and the year A.D. 1 would have waited for the celebration of Christ’s first birthday. That way the year A.D. 1000 would have begun the second millennium and A.D. 2000 would be the beginning of the third millennium. The way things are now we are doomed to endless arguments every time we approach a new decade, century, or millennium.

Actually, only astronomers, with their need for precise and continuous time, are really bothered by Dionysius’s missing zero. And they have merely inserted it where it belongs — as the year before A.D. 1 — and work from a master chronology much longer than 532 years to keep their astronomical dates where they belong no matter what the rest of us decide to do with our all-too-human calendars.

MORE INFORMATION

U.S. Naval Observatory and the Third Millennium
http://aa.usno.navy.mil/faq/docs/millennium.html

The U. S. Naval Observatory says the 3rd millenium will begin with AD 2001 and explains the shortcomings of Dionysius' new timekeeping system.

British National Maritime Museum and the New Millennium
http://www.nmm.ac.uk/server/show/conWebDoc.2939/viewPage/1

This is a 5-part discussion of the new millennium prepared by the British National Maritime Museum to answer the many questions that were coming its way in 2000 and 2001.

Millennium - Wikipedia
http://en.wikipedia.org/wiki/Millennial

The Wikipedia explains the difference between ordinal and cardinal numbers and discusses ongoing debates over when millennia begin and end in considerable detail.

Dionysius Exiguus - Wikipedia
http://en.wikipedia.org/wiki/Dionysius_Exiguus

The Wikipedia offers a substantial explanation of who Dionysius Exiguus (Dennis the Little) was and wasn't, what he knew and didn't know, and what he did and didn't do to Easter dates and his new system for numbering years.