(DM’s note - the following information is taken from the WotC publication Gazetteer)

A solar year is 364 days. Oerth has two moons. The greater moon, Luna, follows a 28 day lunar cycle and governs the 12 months. The lesser moon, Celene is full four times a year, corresponding with the four festival weeks.

A week consists of the following days:

Starday
Sunday
Moonday
Godsday
Waterday
Earthday
Freeday

The twelve months and the four festivals are:

Needfest (midwinter)
Fireseek (winter)
Readying (spring)
Coldeven (spring)
Growfest (equinox)
Planting (low summer)
Flocktime (low summer)
Wealsun (lowsummer)
Richfest (midsummer)
Reaping (high summer)
Goodmonth (high summer)
Harvester (high summer)
Brewfest (equinox)
Patchwall (autumn)
Ready’reat (autumn)
Sunsebb (winter)

Campaign Timeline 

Note - All dates given from the birth of the Great Kingdom, marked as Common Year (CY).

440-490 - Dwarven and elven members of the fellowship are born

560-575 - Half-elven, halfling, half-orc and human members of the fellowship are born

562 - Macsen Wledig founds Kendall Keep 

583 - Macsen Wledig and his army fall to the forces of Iuz in the Shield Lands

588 - Members of the fellowship journey to the city of Dyvers

589 (Patchwall) - Tristan Cambridge, friend to the fellowship, travels to Kendall Keep

590 (Readying) - The fellowship journeys to Kendall Keep after receiving a letter from Ambercrombie of St. Cuthbert (The Caves of Chaos Part 1)

590 (Readying-Flocktime) The fellowship begins battling the evil gathering in the Caves of Chaos and the lands surrounding Kendall Keep (The Caves of Chaos Parts 2-8)

590 (Wealsun) The fellowship leaves Kendall Keep to face the powers behind the Caves of Chaos (The Caves of Chaos Part 9)

590 (Richfest) Dyvers holds open gladiatorial games at The Coliseum