The Arthurian Federation has used its own calendar since it was settled in 910 A.D. The year 910 A.D. is the first year of the Arthurian calendar and is known as 0 A.R. (Arthurian Reckoning) - the year in Arthurian Reckoning can therefore be found by subtracting 910 from the Gregorian calendar. A year in the Arthurian calendar is the same length as that of the Gregorian calendar, that is 365 days, 5 hours, 48 minutes, 46 seconds but the months follow the lunar cycle and are thus split into 12 periods of 30 days. To make up for the shortfall of days, five additional days unaffiliated with any month are added into the middle and start of the Arthurian calendar and a sixth day is included in the midsummer every four years to account for leap years.
The months in Arthurian Reckoning are corruptions of the Ancient Arthurian names, though their meaning can still be understood in modern-day Arthurian. They are based primarily on major agricultural or religious events in the year.
| Month Number | Month Name | Relationship to Gregorian Calendar |
| 2 Jol | 22 December | |
| 1 | Eftirjol | 23 December to 21 January |
| 2 | Solmanuður | 22 January to 20 February |
| 3 | Røda | 21 February to 22 March |
| 4 | Astron | 23 March to 21 April |
| 5 | Trirmalking | 22 April to 21 May |
| 6 | Forlit | 22 May to 20 June |
| 1 Lit | 21 June | |
| Midtenvetur | 22 June | |
| Øferlit | Leap Day | |
| 2 Lit | 23 June | |
| 7 | Eftirlit | 24 June to 23 July |
| 8 | Wodmanuður | 24 July to 22 August |
| 9 | Helogmanuður | 23 August to 21 September |
| 10 | Veturfuldmanuður | 22 September to 21 October |
| 11 | Bloðmanuður | 22 October to 20 November |
| 12 | Forjol | 21 November to 20 December |
| 1 Jol | 21 December |
The Joldag (Yule Days) straddle the new year while the Litdag (Lithe Days) mark the midwinter. Both are placed outside of any month and are primarily holidays and feast days. Midtenvetur (Midwinter's Day) and Øferlit (Overlithe) are not assigned to any day of the week - they are nameless in that sense - and in this way every day of the year retains the same weekday designation from year to year, unlike the Gregorian calendar.
The days of the week are, starting from Saturday in the Gregorian calendar, Stjarndag, Soldag, Mandag, Trejdag, Himildag, Sjordag and Hardag. Hardag is usually a half-day replete with evening feasts and so correlates more with Sunday (Soldag) in most countries, especially those with a strong Christian tradition.
