Millenniums - or should it be millennia? - are very dangerous. In AD 1000, for example, panic spread through continental Europe because many believed that the 1,000th anniversary of the death of Christ would mark the Second Coming. Their fears were nurtured by a famine arising from torrential spring thunderstorms which flattened crops in much of France.
As Radulph Glaber, a contemporary monk of Cluny, put it: "Men thought that the very laws of nature and the order of the seasons were reversed and that those rules which governed the world had been replaced by chaos. The end of the world, they knew, was nigh."
Huge crowds made public displays of repentance and swore to keep the peace of God forever, hoping that Armageddon be postponed - as, indeed, it duly was.
Now, despite the haunting presence of El Nino and disturbing rumours about climate change and global warming, you might think that we were fairly safe at present from impending doom, with no millennium in sight for a year or two at least. Not so! You may well have less than a day to repent your wicked deeds. By some reckonings, the Sixth Millennium will end, and the Seventh possibly begin, at breakfast tomorrow.
Dr James Ussher was Archbishop of Armagh in the middle of the 17th century and his hobby was the study of Biblical "begats". He noted, for example, that according to Chapter Five of Genesis, Adam begat a son called Seth when he was 130 years old and that Seth, in turn, had a son when he was 105. Seth's son, Enos, begat Cainan, and so on to Mathusala and Noah.
Indeed, by continuing this analysis and using bits and scraps of information given in succeeding chapters, Ussher reached a stage where these Old Testament happenings overlapped confirmed historical events. By working backwards he was able to fix the year of the Creation at 4004 BC.
A few years after Ussher made his findings known, another cleric revised and refined these biblical assessments. The Rev John Lightfoot was vice-chancellor at Cambridge University and in his spare time had acquired an even greater expertise than Ussher's in Old Testament "begats".
He redid the calculations and while broadly agreeing with the conclusions of His Grace, came up with an answer that was even more precise: the world, according to Lightfoot, began at 9 a.m. precisely on October 26th, 4004 BC.
If he is right and if you recall that there is no "year zero" in the AD/BC system, it means that the Sixth Millennium will end at 9 a.m. tomorrow.