The Anglo-Saxon Calendar
The Anglo-Saxon calendar is a notional calendar of my own invention, and is an attempt at inventing a calendar that is more in tune with the seasons and takes into account some ostensibly old English traditions. It is inspired by Tolkien's "Shire Calendar", which is explained at the end of the full edition of "The Lord of the Rings". The idea behind the calendar is that it would begin each year on the day of the winter solstice and the months would be arranged so that each subsequent quarter started on or as near as possible to the other solstice and the two equinoxes, but with as simple an arangement of months as possible. This page explains how the calendar works. It is not intended to be a proposal for calendar reform, which I have detailed elsewhere, but just for personal interest, similar to the Shire calendar.
The ancient Anglo-Saxon calendar was reputed to be a luni-solar calendar, following the cycles of the moon and adding an extra month every few years to keep it in line with the seasons. This calendar was reputed to have had its new year on Christmas Eve, however this would not have been possible every year if the calendar were luni-solar, due to the lunar year not matching the solar year. It is thought that the 12 days of Christmas may have been "epagomenal" days added at the end of the year to compensate for this but this is speculative. If this were so, however, then the calendar would have been kept in synchronisation with the solar year through this method without having to resort to adding an embolismic month every few years. It would also, however, have meant that the months would have had no relation to the lunar cycle, so in effect it would have actually been purely a solar calendar. This is effectively what happened with the Roman calendar when it was converted to a solar one by Julius Caesar in 45 BCE.
So, the calendar I have devised is a solar one using Anglo-Saxon month names, in a similar vein to Tolkien's Shire calendar, as mentioned above. It begins each year on the day of the winter solstice, with the Yuletide period being the most important festival of the year, generally lasting for 12 days from the first day of Afteryule, the first month. Whether a year is a leap year or not depends on how many days there are between successive winter solstices, so it is entirely based on astronomy rather than a fixed pattern of leap years, and future years are predicted using computational algorithms. These, of course, can prove to be inaccurate over long periods of time, however, so the actual pattern of years would be based on the actual astronomy at the time, rather than on the predictions, thus the calendar is flexible enough to cope with changes in the Earth's mean tropical year between winter solstices. In addition to this, the computer predictions are accurate enough for a window of sevral hundred years on either side of the time that they are made, which is all that is required for practical purposes.
Structure of the calendar
As mentioned above, the calendar is arranged to begin on the winter solstice, and the months are organised so that the other quarters of the year (or seasons) begin on or as near as possible to the actual equinoxes and solstice as possible. Originally, the calendar may have had flexible months that changed length according to the seasons, with each month covering 30 degrees of the sun's movement through the sky each year, rather like the major solar terms in the Chinese calendar. This would have meant several months fluctuating in length from one year to the next, so this has given way to a more practical system of standard month lengths, and only one variable month that receives an extra day in leap years. In the modern calendar there are in fact only two lengths of month, 30 or 31 days, and in leap years one of the 30-day months gets the extra day, making it another 31-day month. This means that the official seasons of spring, summer and autumn do not always coincide with the start of a Saxon month, but on most occasions they do or are at most there is a day of a difference. The following table shows the months with their lengths and their most common starting dates in the Gregorian calendar (leap years shown in curly brackets).