The Old English Solar Calendar

The Old English (or Anglo-Saxon) Calendar

The Old English calendar is a notional calendar that I have invented for my own personal use and interest. It is not intended to be a proposal for calendar reform.

There is evidence that a calendar like the was used in Saxon times, with similar names for the months. What is not really known is whether it kept time with the solar events of the year, as mine does, or whether the names were, in fact, just alternative names for the months in the Julian calendar, as the standard calendar was known in those times. My calendar uses these Old English month names, alongside conjectural modern English derivations of the same. I have also taken inspiration from Tolkien’s “Shire Calendar” in deciding on the names and timings of the months. Finally, there is an astrological connection in that I have decided that the calendar should be based on annual solar events, and thus the months tend to coincide reasonably closely with the periods covered by the signs of the zodiac, e.g. Solmonath coincides roughly with Aquarius.

How it works

The ancient Old English calendar was reputed to be a luni-solar calendar, following the cycles of the moon with an extra month added every few years to keep it in line with the seasons. This calendar was reputed to have its new year on Christmas Eve, but this would not be possible every year if the calendar were luni-solar, as 12 months in a lunar calendar are only around 354/5 days as opposed to the 365/6 days in a solar year. It may be that extra, or “epagomenal”, days were added to the end of the year account for the difference, and that these were the origins of the 12 days of Christmas, but this is not known for sure.

The calendar I have devised, however, is purely a solar one using Old English month names, in the same vein as Tolkien’s “Shire Calendar”, which itself is based upon details of a pre-Christian calendar by Bede, in his work De temporum ratione (“The Reckoning of Time”) in AD 725. The calendar year has either 365 or 366 days depending on whether the year is common or leap. The year starts at midnight on the longest night of the year, i.e. the midnight nearest the northern winter solstice (in this article this is called the south solstice as it is when the sun reaches its most southerly latitude). This means effectively that if the solstice occurs before noon G.M.T. on 21st December, then that is the first day of the year, but if it occurs after noon G.M.T. then the next day is the first day of the year. Subsequent seasons start on or a day before the first day of each quarter, so the months coincide roughly with the periods of the signs of the zodiac and each quarter with the four seasons.

The following table shows the months with their lengths and their usual start dates in the Gregorian calendar in the present period. These dates can vary by a day or so either side of the given dates due to the different cycles of leap years between the two calendars. Leap years in the Old English calendar depend on the number of days between each winter solstice, and in those years where there are 366 days between these days, an extra day is added to the month of Solmonath, making it 30 days long. Therefore there is no simple arithmetic leap rule in this calendar, the leap years occur as and when they are required, which is usally every four years but sometimes there is a five-year gap.

Name Usual starting dates Days
22 December
21 January
29 {30}
19 February
21 March
21 April
22 May
22 June
23 July
23 August
23 September
22 October
22 November

Note that the months of Aergiuli (Foreyule) and Aeftergiuli (Afteryule) do not mean before and after Yule, but “Early Yule” and “Late Yule”. This is because originally there was a “Yule Month”, which was split between the early and late parts. The same is true of Aerlitha (Forelithe) and Aefterlitha (Afterlithe).


The epoch for the calendar is the year 444 C.E. and the era is called A.S.E. (Anglo-Saxon Era). The year numbers are therefore approximately 444 years behind those of the Gregorian calendar.

The Days of the Week

The days of the week were named after Norse deities, apart from Saturday, Sunday and Monday, and have the same origins as the names that are still used today. The Old English names for the days of the week were: Sunnandæg, Monandæg, Tiwesdæg, Wodnesdæg, Þunresdæg, Frigedæg, and Sæternesdæg.

Holidays and Festivals

The main festive days observed in the calendar are as follows, with typical equivalent dates in the Gregorian calendar:

  • Modraniht (Mothers’ Night), 30 Aergiuli (21st December)
  • Yule Day, 1 Aeftergiuli (22nd December)
  • Yuletide, 1 – 12 Aeftergiuli (22nd December – 2nd January)
  • Winter Cross Quarter, 15 Solmonath (3rd February)
  • Ostara, 1 Eostremonath (20th – 21st March)
  • Egg Moon (Movable – first full moon of spring, usually occurs in Eostremonath)
  • Spring Cross Quarter, 16 Thrimilchi (5th May)
  • Litha, 31 Aerlitha – 1 Aefterlitha (21st – 22nd June)
  • Summer Cross Quarter, 16 Weodmonath (6th August)
  • Harvest Moon (Movable – last full moon of summer)
  • Mabon/Harvest Home, 31 Halegmonath (22nd – 23rd September)
  • Autumn Cross Quarter, 16 Blotmonath (6th November)

In popular parlance, the Harvest Moon is the full moon closest to the autumnal equinox, therefore it could occur in the last half of Halegmonath or the first half of Winterfylleth. In more northern climes, however, harvest would tend to occur earlier than this, and this fits with it being the last full moon before the equinox in my calendar. This means that it will usually fall in the month of Halegmonath, which, interestingly enough, has the alternative name of “Harvestmonth” (Haerfestmonath).

More on Leap Years

The rule for leap years is simple – if there are 366 days between one winter solstice and the next, then the year is a leap year. To calculate the date and time of the northern winter solstice I have used the method detailed in Jean Meeus’s Astronomical Algorithms, 2nd Ed., Ch. 27, which gives results to an accuracy of within a minute for dates between 1,000 and 3,000 C.E.

The following table shows the occurrence of leap years for the period 2020-2040.

Incidence of leap years in the Old English Calendar, 2020-40 C.E.
Tracking the Seasons

Basing a calendar on an astronomical event such as the winter solstice or the vernal equinox requires the ability to predict the future dates of these events, if it is desired to project the calendar into the future. The problem with this is due to the way the Earth spins – it has a “wobble” that means that the seasons move in relation to the background constellations in the sky. But probably more importantly, the apsides, which is the collective name for the perihelion (the closest point of the Earth’s orbit to the sun) and the aphelion (the farthest point of the Earth’s orbit to the sun), move in relation to the seasons. This means that the seasons are different lengths and these lengths change over time. For example, the perihelion currently occurs in early January, but a few centuries ago it occurred at the time of the northern winter solstice, and in a few thousand years it will move into February and eventually occur around the time of the vernal equinox.

This means that winter in the northern hemisphere is currently the shortest season, because the Earth moves faster in its orbit around perihelion, and it will get shorter until the perihelion reaches early February. Once it reaches the vernal equinox then winter and spring in the northern hemisphere will be equal in length, and summer and autumn will be longer, but also equal in length. Due to these changes, if the calendar is to be kept aligned to the seasons, adjustments will have to be made to the lengths of the months in this calendar in the longer term. This, however, will not concern us in our lifetimes.

As this is a complex subject, I will not go into further detail here, but the links below provide some very interesting reading, with graphs to show the long term trends in the seasons and how calendars can use some simple rules to track them.