Within the world there two well respected calendars. The Rashidian Calendar, and the Khetian calendar. Both are of works of Dwarven scholarship, with the Rashidian calendar simply resetting the year to 0 at year 4057 of the Khetian calendar. In general, dates are marked as follows.
Ky4387 = year 4397 of the Khetian calender
Ry240 = year 240 of the Rashidian calender
Since the Rashidian calendar is the one in general use in the year Ry240 many simply refer to time using the number only, with the Ry being assumed. All formal documents still use Ry however.
The Doann are believed to have held some sort of calendar system prior to The Danegian Conquest, but knowledge of it is long lost and the Doann simply use the Dwarven calendars without complaint.
The Airen are not know to have held any formal calendar system, and they seldom bother dating events. They will at times use the Danegian calendar, but generally simply refer to the event in relation to their age at the time, and generally care little for events transpiring before their lives began.
The Doar are believed to have had some sort of basic calendar system, but knowledge of it was lost during The Wars of Elevation.