Westminster, London, 21st December 2013, The Winter Solstice
The last three blogs have been about the three celestial cycles of time most important to us as humans: the day, the year, and the moon phase.
All these cycles can be quite a problem for calendar inventors and watchmakers alike, for the simple reason that they’re not in sync with each other at all. The seasons repeat about every 365.2422 days, with a little bit of wobble; the tides on average every 29.53059 days, with a lot of wobble. (Honest, all those digits really are necessary, otherwise we would soon get out of kilter with cumulative errors.)
Historically, calendar makers have tried to synchronize days either with the sun or the moon, but not both. The Islamic calendar follows the moon, which is why Ramadan is around 12 days earlier each year. Julius Caesar’s 365-day calendar, more widely adopted, follows the sun and allows a 366-day leap year every fourth year.
This almost, but not quite, gets the sun's cycle right. It was only in Pope Gregory XIII’s time (1500’s) that the error was noticed. He decreed not only that three leap years every four centuries should be skipped, which gives a startlingly accurate calendar, but that the extra leap days that had built up over the centuries had to be skipped, to make up for lost time.
The new system was a while in percolation. In Britain – we were late adopters – it took until the second of September 1752, which was followed by the fifteenth of September. According to Hogarth, people took to the streets, demanding their days back.
That decade was a heady time for British watchmaking for other reasons, too. Graham invented the sweep seconds hand. Harrison, temperature compensation. Mudge, the lever escapement. Just don’t ask any of them what they were up to on 10th Sept ’52, because there wasn’t one.