In designing my home-brewed Erseta campaign (which is finally kicking off in about an hour and a half!), I wanted to avoid a common pitfall I see in any number of fantasy settings. Overly rational calendars.
In too many campaign settings, calendars are either ignored (leaving the game master to come up with something on his own and hope that the setting’s designer doesn’t come up with something completely at odds later on) or are too “easy”. Months are all exactly the same number of days, which happen to be divided into full weeks, and the sun and moon(s) obey the clockwork precision needed for the game master’s calendar to be perfectly symmetrical, orderly, and reusable in all years.
Historically, calendars are very messy things. The orbits of heavenly bodies rarely acquiesce to humanity’s love of even numbers and symmetry. Not every civilization had weeks of seven days (or even weeks at all), and many were constantly tinkering with their calendars to make them more accurate, less complex, more in line with nature or what religious teachings taught about nature, or even for use as political tools. Even the most basic things, such as when the year actually begins, are subject to change.
Even the modern Gregorian calendar wasn’t adopted until 1752. To this day it’s not universally accepted, and some still use the Julian calendar or some other calendar altogether (Chinese, Muslims, Hindus, Jews, etc.).
So for my campaign I wanted something messy. Something that had a little character. So I came up with this (click to embiggen):
Erseta’s year is 373 days long. The High Church follows the old Erian calendar, which consists of a number of months of varying lengths plus several intercalary periods (note that Lithalia takes place in the middle of Sunmonth, and Mabonalia takes place in the middle of Witumonth). No “weeks” are used, and there are no “generic” names for days. Dates are calculated from the beginning of the month, and years are counted from the founding of the city of Eria. Example: The reign of Duke Roginald of Archanaovis began on the 11th day of Brachmonth in the year 1529 AE (After Eria). In this, it’s somewhat like the old Roman calendar, and I consciously used an ancient Roman calendar as the model for how this calendar is presented.
The moon follows a cycle of 32 days, constantly shifting in appearance and shape as it goes through its phases and slowly rotates to reveal its entire surface (it is not tidally locked, and thus does not always present the same face to the world). Indeed, a whole science of lunology has developed which predicts future events based not on the movements of the stars (although astrology is also practiced) but rather by which features are visible on the moon during which phases. The dates of the various cycles of the moon vary from year to year, but the solstices and equinoxes are constant.