The Calendar of Britannia is structured as following:
The Britannian year is a little shorter than the Earth year with 336 days, meaning that Britannia's orbit around its sun is a little closer. The year is divided in 12 months which are divided into 4 weeks of 7 days. Each day is divided into 24 hours. The hours, minutes and seconds are the same as on Earth, as proven by an Earth Pocketwatch.
The length of the month can be measured by the calendar display in Ultima VI. The month is adjusted to the cycles of the Moons Trammel and Felucca, so that the first of a month -and therefore the first of a year- always falls on double new moon, which only happens once a month. This also means that the Astronomical Alignment can only happen during the first of the month at double new moon.
The months have the same names as on Earth's calendar, possibly thanks to Lord British:
The year count starts with the founding of Britannia, which happened sometime between Ultima III and Ultima IV. By Ultima V it was the year 139 (calendar display). The start of Ultima VI is in 161 (again calendar display). Ultima VII takes place exactly 200 years later, thus in the year 361. It is unknown if Britannia has leap years, in which extra days are added. Considering that the lunar cycle and calendar days probably don't match up perfectly, this would very likely correct any errors that appear over time.
The cycles of the moon during the month are as follows:
There are two inconsistencies in the system:
- In Ultima V, the year actually has 360 days with 30 day months. This was probably scrapped since it created chaos with the lunar cycle.
- In Ultima IV, a double full moon was possible, something that is no longer possible in the final system.