Most cities have little in common, other than the same coin-types, languages and their understanding of time. While the months, weeks and days may wary, the years are all used in the same way; as all were under Giant rule when the calendars started.
B.C. (Before Civilization)
The B.C. calendar is the earliest one (though Mountain Dwarves have recorded dates way before this), it counts downwards, which sometimes can confuse those not great with numbers (or books), but the B.C. calendar ends with 1, where it starts is unclear, as not many things still stand from the time before the Giants. Most significant occurrence was the start of the First War against the Giants, starting with Karan’s rebellion in 216 B.C.
A.Y. (Abborgardian Year) Sometimes the abbreviation AoA is also used in it’s sted (Age of Abborgard)
Where the time before civilization ends, the time of the magocracy known as Abborgard begins. Until the rise of the mages, most fighting had been just that, and only through tactics and numbers, had the armies of Humans, Gnomes and Halflings been able to make any progress. With the use of magic, the battles suddenly became a lot easier, and a final succes was had at the Battle of Grunnmr, where a vast Giant army, led by Cromm the Warlord, fell. This marks the year 1 A.Y. The time of Abborgard was one of peace and prosperity, as the mages enabled trade from the northern territories to the southern lands, inviting Tiefling and Dragonborn into centrall Fellmir. The Abborgardian calendar ended on 605 A.Y., the 13th of Highsun, with Abborgard’s Collapse.
A.A. (After Abborgard)
After Abborgard’s fall, many alliances were broken. Chaos rose, and darkness is waiting to break the light of day forever. Orc war-parties grow ever bolder in the north, Gnolls attacking merchants with silver from Ezolder, and in Grunnmr… The Giants might see chance for a brutal revenge.
The current year is 48 A.A.