Time to change your calendars and diaries over! Happy new calendar day for MMXI!
The Sun and the Year
It takes the Earth 365.24219 mean solar days to orbit the Sun once. This is slightly more than our nominal 365 day long year, so every four days we have a leap year, with 29 days in February instead of the usual 28. This still isn’t quite right, so the last year of every century is not a leap year unless the year is divisible by 400, which is why 2000 was a leap year but 1900 wasn’t.
There are four key points in the Earth’s yearly journey around the Sun.
The Solstices are where the Sun appears to stand still at solar noon for a few days, this means that it is in the same position in the sky at solar noon. Solstice comes from the Latin sol for Sun and sistere which means to stand still. Around the 21st December each year, the Sun is the furthest south from the equator in the sky and we in the northern hemisphere experience the Winter Solstice, the shortest day in the year. Around the 21st June, the northern hemisphere’s Summer Solstice occurs, with the Sun being at it’s most northerly from the equator. This is the longest day of the year for us.
The Equinoxes occur in between these points. The Vernal Equinox occurs around the 21st March and the Autumnal Equinox around the 21st September each year. On these days, the Sun is directly over the equator. These are days where the hours of daylight and night are approximately equal, and the word equinox comes from the Latin equi meaning equal and nox meaning night.
To our modern eyes, the cycles of the Sun are important in terms of determining the seasons, the weather, agricultural practices and so on. But that wasn’t always so.
The Moon and the Year
To early man, it was the Moon, with its cyclical waxing and waning that was the more obvious object to use to measure time and all the earliest known calendars are lunar, based on the phases of the Moon. Indeed, the word month comes from the use of the phases of the Moon to split the year up into segments.
It takes long and complicated sums to link the cycles of the Moon to those of the Sun. A lunar month is 29.5306 days long, so a twelve month lunar year would last just over 354 days and so is around 11 days out of step with the Solar year. If we were to follow a lunar calendar, it would take just about 16 years for the seasons to be completely reversed.
Julius Caesar and the 1st January
Whatever the religious reasons may have been to keep to a lunar calendar, it must have been obvious that it was the cycles of the Sun that had the biggest effect upon human activity. It was the turning of the seasons that determined when crops were to be sown, when they were due to be harvested, when the weather would be good enough to set sail, and for so many other things too, yet the lunar calendar was still in use, with all the problems of errors and corrections that needed to be made until the Julian calendar was introduced by Julius Caesar in 45BC.
Caesar learned of this calendar from the Egyptians. Legend has it it was at a party thrown by Cleopatra in his honour. The Julian calendar was based on a 365 day year, with an extra day thrown in every 4 years. Each year had twelve months with thirty or thirty-one days, except February, and the 1st January was set as the beginning of the year.
The calendar as we know it today was now more or less in place. It was regular, secular and based on the real movements of the Sun.
Emperor Constantine (d. AD377) imposed Christianity as the major religion of the Roman Empire and he placed the design of the calendar back in the hands of religious groups who were still wedded to the traditional lunar movements for their major festivals. After the collapse of the Roman Empire, the Christian church was the nearest thing to an international controlling committee and the West entered a long, dark time where scientific enquiry was frowned upon at best and considered heresy at worst.
The Gregorian Calendar
By the C16th, the western world was stable enough to attempt to reform the calendar. The small errors from the Julian calendar had now become noticeable and annoying. In 1582 Pope Gregory finally announced changes in the calendar to correct these faults and prevent them from happening again, including the 400 year rule for leap years mentioned previously.
He introduced what became known as the Gregorian Calendar, and ordained that 5th October should become 15th October to bring the calendar back in line with the physical world. This was a much needed and a sensible solution to the problem of the calendar.
However, the changes were not universally accepted, especially in Protestant countries such as Britain. The changes were declared to be a ‘Popish plot’ designed to undermine their credibility. For more than a century following this Papal decree, half of Europe was 10 days ahead of the other half!
It took Britain until 1752 to adopt the changes, by which time it had to correct the calendar by 11 days to bring it back into line with Gregorian calendar. Philip Stanhope, fourth Earl of Chesterfield, initiated this move by introducing a Bill to correct the ‘inconvenient and disgraceful errors of our present calendar’. This Bill was signed into law by George II on 22nd May 1752. Chesterfield’s Act decreed that Wednesday 2 September 1752 be followed immediately by 14 September 1752 and also that the New Year was to start officially on 1st January.