Until the early 5th century, there was no unified calendar across all the Jarrow crown lands. Variants included a nocturnal counting system in the Jarrland forests, a lunar calendar in the Kornandon territories of Farridon, zodiacal reckoning by boat clans, and a solely seasonal calendar used by the sylphids. On top of this, almost every clan and territory had its own names for the months, making communication and organisation a nightmare.

To assist with integration of new territories, in 415 King Athelmere unveiled a new calendar to be used universally. The new calendar was based on that of the Jewelled Cities and includes twelve months of thirty days, with a five-day holiday week. The month names are derived from the old Elven language as understood by Jarrland scholars. Unlike in the Islander calendar, the Merian holiday week covers the winter solstice rather than the summer; the two calendars therefore align, albeit the months may be differently numbered.

For ease of adoption, some local names for the months are used in newer territories. Tempestia uses two localised names based on native culture, and the Kornandon of Farridon have their own name for each month. The calendars are otherwise identical.

The Salterri calendar is still used at a governmental level to calculate dates for purposes of tribute. Some local calendars may remain in operation on an informal basis, but all communication from the king now uses the Merian system.

Month # Standard Name Sylphid Name Kornandon Name Notes
- Luhikhet Bersizun 5-day week, Winter Solstice
1 Kauhemand Fallmiz
2 Kaevamand Toullanmiz Salterri Moonshroud Festival (Biannual)
3 Metsikmand Gouemiz Spring Equinox
4 Kasvamand Humamand Plantamiz
5 Sugumand Revelmiz Kevadag (Fertility Festival)
6 Adermand Aramiz Summer Solstice
7 Luhtmand Peurvanmiz
8 Kunnimand Brudmiz Kroondag (Coronation Day)
9 Veinmand Gwinmiz Autumnal Equinox
10 Jahtmand Tormand Chasemiz
11 Overdamand Kigermiz Langendag (Remembrance Festival)
12 Hallmand Rewimiz