If you want to know the time, argues Robert Poole, you should ask an historian.
The approach of the Millennium has created a wave of interest in the history of the calendar. When does the millennium really end? Does it matter? Is the calendar actually right? Whose calendar is it anyway? The more you look at these questions, the more complicated they get. I will try to offer straightforward answers, based on historical rather than merely mathematical or rational perspectives.
When does the millennium end?
The end-of-the-millennium question shows the limits of a purely rationalist approach to the calendar. You don't have to go very far into these arguments to realise that mathematical solutions have their limits. Rational people can become quite rigid on the millennium issue. Only the ignorant, they insist, will take any notice of the year 2000, since we shall still be in the twentieth century until it ends. The first millennium began on 1 January AD 1; the second millennium began on 1 January 1001; the third millennium will therefore begin on new year's day 2001. Years are grouped in tens, starting with one and ending with ten, for there was no year zero.
All that is logical enough, but the calendar was not designed and set running by a technician at midnight on 1.1.0001; it developed historically. Certainly there was no year zero. But nor was there ever a year one, two or three, or for that matter a year 100, 200 or 300. The Christian calendar was devised as late as the sixth century AD by a Scythian monk, Dionysius. Asked to calculate the correct date of Easter by the Pope, he went back to first principles and fixed a new base year for the calendar: the year of the birth of Christ, which he called Anno Domini (the Year of our Lord) 1. The Christian calendar was what is known as a 'retrofit', and a rather awkward one at that, done a full five centuries after the epoch it was meant to fit.
The AD system superseded the previous system of dating from the reign of the Roman emperor Diocletian, the Christian 'age of the martyrs' which had finally forged the faith. But in determining the birth of Christ, Dionysius had to wrestle to combine defective historical records with the ambiguous evidence of the Bible. St Matthew's gospel, for example, states that Christ was born in the time of Nero, who we now know died in 4 BC. If there was an historical Jesus, scholars now reckon he was most probably born around 4 or 5 BC.
There are other uncertainties about the start of the Christian era. 1 January is not the date of Christ's birth, but the feast of the circumcision. This meant a lot to the early generations of Christians within the Jewish tradition, but after the victory of Roman-style Christianity this was ignored in favour of a birthday commemoration fixed to the pagan midwinter feast of 25 December, timed to mark the approximate point where the days start getting longer after the winter solstice. On one reasonable calculation, Christ was born in the year 1 BC, which means the millennium would indeed fall in the year 2000, on Christmas day.
The basic thing to understand about the calendar is that it is a human, not a natural, construction. There is no single universal measure of time. We take our time from the movements of the heavens. It works fine for us, but if there is ever first contact with aliens we are unlikely to find that they set their calendars according to the motions of the third rock from the sun. Even from our vantage point, this way of measuring time has its problems.
The day is the commonest and most straightforward measure of time. But days are not equal in length because the earth's orbit is elliptical; when the earth is on the steeper part of its curve, it gets a bit further round the sun in one rotation than when it is on the shallow part of its orbit. The time measured on a sundial can be anything up to a quarter of an hour ahead or behind the time measured by a clock, the amount varying with the seasons. Our day is an average day, accurate by the clock only four times a year. The day, at least, is universally recognised on earth. Longer measures of time present other problems. The week of seven days is a purely human invention, with no equivalent in the motions of the heavens; its widespread use testifies only to the enormous influence on history of the ancient Babylonians, who invented it. The month is roughly lunar, but only roughly; a lunar month is 29-and-a-half days, and there are twelve-and-a half lunar months in a year. The year is solar, one turn of the earth round the sun, but it fits none of the other measures; whether you divide it by days, weeks or months, there is always a bit left over – hence leap years.
The western calendar is essentially that adopted by Julius Caesar in 45 BC. The Roman calendar in his day had got badly out of synch with the heavens, so much so that the rites of the spring equinox in March were happening before the winter solstice in December. Caesar, using his dictatorial powers, put in one year of 446 days to bring all to rights, and then instituted the current system of twelve-month, 365-day years with a leap year every fourth year. When Constantine Christianised the Roman Empire in the fourth century AD, the Roman calendar became the Christian calendar. It was adopted as such in AD 325, at the first General Council of the Christian church at Nicea, in what is now western Turkey.
Caesar's estimate of the year at 365/ days was remarkably accurate, but it was still eleven minutes too long. By the sixteenth century the error had accumulated to ten days. The main problem was not the drifting apart of natural seasons and calendar dates; this was too slow to be an issue for any particular generation, and as long as it was the same everywhere, no-one seemed to mind. The issue that bothered the Church of Rome was that Easter was supposed to fall on the first Sunday after the first full moon, on or after the spring equinox (March 21st). The slippage of the seasons meant that it usually did not, and this apparent error in the practice of the Christian world was becoming an embarrassment. In 1582 Pope Gregory XIII corrected this in a bull, or edict. This removed ten days from October 1582, revised the method for the calculation of Easter, and modified the system of leap years, restoring the leap year at the end of every fourth century to keep the new calendar in line with the heavens for the next few millennia.
The Gregorian calendar reform was one of the last acts of the counter-reformation, done in the hope that if a basic agreement could be secured across Christendom on one issue at least, this might assist a long-term re-unification of the various Christian churches. However, the Gregorian calendar was rejected in most of the protestant world until the eighteenth century; protestants then would no more accept the Pope's authority to reform the calendar than we would accept the Ayatollah's. In England, it had been illegal to publish any papal bull ever since the bull of 1570 declaring Queen Elizabeth a heretic and offering a spiritual reward to her assassin. In any case, there was a compelling protestant argument that the calendar should have been reformed by an extra day or two, to the time of Christ, rather that of the Council of Nicea.
Protestant countries would only accept the Gregorian calendar once the calendar came to be seen as a scientific, rather than a religious, issue. Most protestant countries adopted the Gregorian calendar in 1700, although they were careful to adopt their own, astronomically based, definition of Easter. England, where anti-popery remained strong thanks to the 'Popish plot' panic of 1678- 81 and the traumatic rule of the Roman Catholic James II, declined to follow suit.
It was 1752 before it was politically safe to bring the calendar in Britain in line with that on the continent, and even then it was done in a private bill by Lord Chesterfield. The prime minister, the duke of Newcastle, was worried and warned Chesterfield 'not to stir matters that had long been quiet', while the even more timid Archbishop of Canterbury had to be carefully smoothed over by the adoption of a specifically Anglican method of calculating the date of Easter. To this day, the Anglican and Roman Catholic Easters are calculated by different methods, although the Church of England has always ensured that the result is the same, Orthodox countries only adopted the reform in the early twentieth century, under secular, westernising governments; in Russia, the October Revolution became the November Revolution in the process.
Famously, we are told that on the introduction of the Gregorian calendar to England 'the mob' rioted, crying 'give us our eleven days!' in the belief that their lives were being shortened by the loss of eleven days in September. I have elsewhere shown that this long-lived myth is just that – a myth, based on a satirical print of an election mob by Hogarth, and appealing to the widely-held view that the English plebs were ignorant and riot-prone. But it makes a good historical story, and every publication on the calendar, from the venerable Oxford History of England to the new and authoritative Greenwich Guide to Time and the Millennium repeats it. It will probably be around at the start of the fourth millennium, long after my work has been forgotten, for this is one case where fiction really is more exciting than the truth.
Time is relative
There was no absolutely right way of reforming the calendar. The Orthodox churches of the East continue to observe an Easter calculated according to the Julian calendar, which usually falls several weeks before the Roman and Anglican Easters. The Jewish feast of the Passover, originally timed to arrive with the greening of the first ears of' corn, now usually falls in early spring. The Jewish year is based on lunar months, with an extra one inserted at irregular intervals to keep the new year somewhere in the early autumn. The Islamic year is entirely lunar, with the new year drifting gently through the seasons at the rate of about fifteen days a year; from this point of view it is the sun, not the moon, that is irregular.
So, after all that: when does the third millennium century begin? This is question of little interest to Jews, who will be starting the year 5761 in the autumn of the year 2000, or Moslems, who will be starting the year 1421 in the spring, on a date which will depend upon the exact observation of the new moon at Mecca. But if you want a definite answer, I can offer a choice of three. If fidelity to the imaginary baseline of the calendar really is more important to you than that hypnotic moment when all the nines turn to noughts, then you'd better stay in bed: taking the best estimate of Christ's birth as 4 BC, the millennium has already begun. If you want to commemorate the two thousandth anniversary of the birth of Christ at some appropriate but not necessarily exact moment, Christmas day 2000 is as good a date as any.
If, however, you are happy to adopt the view of a social historian that the millennium is a human and not a divine or a mathematical event, then you will probably decide that the millennium is when the party happens. See you at Greenwich!