When Gregory lost 10 days

It is not uncommon for politicians, when they take up office, to complain that their predecessors have left the country in an…

It is not uncommon for politicians, when they take up office, to complain that their predecessors have left the country in an economic mess. Two thousand years ago, however, when Julius Caesar's turn came around, his problems were not with the economy: he found the Roman calendar eight weeks in arrears.

The origins of the difficulty lay in the inconvenient fact that the year, as we know today, is about 365.24219879 days long. Before Caesar's time, the Romans' standard year was 355 days, or close to 12 full lunar cycles. This, of course, was very much too short, so every second year they inserted an extra month to bridge the gap. The whole arrangement, eccentric though it was, came very close to being right on average.

Caesar, however, discovered that the Pontifical College in Rome, whether by neglect or otherwise, had failed to announce the extra month on no fewer than three separate occasions. Not a man to shirk his public duty, Caesar decided that thenceforth there would be a new standard Roman year of 365 and a quarter days.

To bring things back to normal, he added three extra months to 45 BC, making it the longest year in human history, and to make up the odd quarter he decreed that every fourth year should have an extra day. Thus things remained for 1,600 years.

READ MORE

But Caesar's year was not exactly right; it was longer than the solar year by 11 minutes and 14 seconds, so by the 16th century the year, once again, was 10 days "slow" compared to the sequence of the seasons. This time the reformer was another leading citizen of Rome, Pope Gregory XIII. He was advised that the calendar would be very nearly right if three out of every four centennial years were common years, in other words, not leap years.

Accordingly, by papal bull issued in February 1582, it was decreed that a centennial year should not be a leap year unless it was exactly divisible by 400. Backed by the power of Rome, the Gregorian Calendar we now use was introduced almost immediately throughout Catholic Europe; 10 days were skipped to bring it into line, and put the seasons in their proper place.

But the Protestant nations of Europe were recalcitrant. The Gregorian Calendar was not adopted in Britain - and therefore Ireland - until 236 years ago today. By then it was necessary to lose 11 days to bring the seasons into line, and so, to the great annoyance of the general populace at the time, the day after September 2nd, 1752, became September 14th.