Common Year

The Common Year calendar (CY) is the most commonly used datekeeping system in the Flanaess continent of Oerth.

Annual cycle

The calendar of most peoples the Flanaess is based on the lunar cycle of two celestial bodies: Luna, the largest moon, which has a 28-day cycle of waxing and waning; and Celene, the blue moon, which has a 91-day cycle. One year is exactly 364 days long.

The common Flanaess calendar has a seven-day week: Starday, Sunday, Moonday, Godsday (traditionally the day of worship), Waterday, Earthday, and Freeday (traditionally the day of rest). The other days are traditionally work days.

One year consists of 52 weeks, divided into four 13-week quarters. Each quarter begins with a one-week festival when Celene is full, and is followed by 3 four-week months.

Other calendars

The year 1 CY is equivalent to the following dates in other calendars historically used in Oerth:

• Oeridian Record (OR): 645
• Olman Lunar (OL): 805
• Touv Calendar (TC): 1409
• Flan Tracking (FT): 2151
• Baklunish Hegira (BH): 2660
• Olven Calendar (OC): 4463
• Suloise Dating (SD): 5116

Conversion between calendars

	To CY	To OR	To OL	To TC	To FT	To BH	To OC	To SD
From CY	—	+644	+804	+1408	+2150	+2659	+4462	+5515
From OR	-644	—	+160	+764	+1506	+2015	+3818	+4871
From OL	-804	-160	—	+604	+1346	+1855	+3658	+4711
From TC	-1408	-764	-604	—	+742	+1251	+3054	+4107
From FT	-2150	-1506	-1346	-742	—	+509	+2312	+3365
From BH	-2659	-2015	-1855	-1251	-509	—	+1803	+2856
From OC	-4462	-3818	-3658	-3054	-2312	-1803	—	+1053
From SD	-5515	-4871	-4711	-4107	-3365	-2856	-1053	—

Note: None of the calendars of Oerth use a year zero, which complicates date conversion involving negative years since standard mathematics assumes a zero. This occasionally confuses even formal historians. The solution is to add 1 when converting from a negative date to a positive, and to subtract 1 when converting a positive date to a negative. If both dates are negative, no adjustment is necessary.

Other worlds

The year 591 CY is approximately equivalent to 1372 DR, or Dalereckoning, the calendar of Faerûn. Mordenkainen, the archmage of Oerth, is known to have met Elminster around this time.

The year 578 CY is approximately equivalent to 1985 AD, or Anno Domini, the calendar of a world known as Earth.

Conversion between the timescales of worlds is not necessarily direct or linear.

History

The Common Year calendar was established by Grand Prince Nasran of the Great Kingdom of Aerdy, who declared himself first Overking of the Great Kingdom in that year. It replaced the previous calendar, the Oeridian Record.

Creative origins

When Gary Gygax published The World of Greyhawk Fantasy World Setting (1980), he included a brief timeline of historical events in order to explain how the Flanaess had arrived at its present state of affairs. This included the Common Year calendar.