Continuity/Auberean, Ispar, and Time

In-game Calendar
The developers of AC created a unique time system. However, the in-game calendar is incorrect. First, the date given varies by server. At the time of this edit (July 24th 2010) the following dates were displayed on each server: Since the dates vary by server it cannot be used as a reliable measurement. Second, the dates on the calendar progresses at a faster rate that dates given in lore. In game, a full day-night cycle lasts a matter of hours. The rest of the in-game calendar is based around this. However, in lore terms one year in the real world and one year in Dereth are equal. For example, in Dereth there are only four seasons per real world year instead of per in-game calendar year. And most importantly, whenever the PY is referenced in lore, it is written in the correct year (For example 1999 = PY 10, 2009 = PY 20).
 * FF: Morningthaw 24, 132 P.Y.
 * HG: Frostfell 29, 131 P.Y.
 * LC: Morningthaw 2, 163 P.Y.
 * MT: Wintersebb 4, 180 P.Y.
 * SC: Wintersebb 30, 124 P.Y.
 * TD: Leafdawning 29, 133 P.Y.
 * VT: Thistledown 6, 79 P.Y.
 * WE: Snowreap 6, 117 P.Y.
 * DT: Leafcull 11, 131 P.Y.

Conclusion
The in-game calendar is no correct. It is likely that the calendar panel has not been corrected since it is a minor issue, and fixing it would could potentially interfere with the day/night system. For the correct Portal Years and Roulean months as they correspond to the patches and real world dates, see Patches.

Yalaini Eipothi, Portal Years and the Roulean Calender
There are three major calendar systems in the lore that we have useful information about: The Yalaini Eipothi, the Portal Year system, and the Roulean Calender. The Yalaini Eipothi measure years on Auberean. This calendar system is broken up into Eipothi, or epochs, with a new Eipoth declared by the ruler of the Seaborne Empire of Yalain at the mark of a great event in history. For more information see Yalain: Eipothi. Portal Years measure time on Auberean. This is an Isparian calendar system, with Portal Year 0 begin after Elysa and Thorsten's band defeated the Olthoi Queen. The Roulean Calendar (RC) measures years on Ispar. In the Ages of the Empyrean article found on the AC:DM CD Lore we are given the following inforation:


 * bgcolor=#d0d0d0| '''Eipoth
 * bgcolor=#d0d0d0| '''PY
 * bgcolor=#d0d0d0| '''RC
 * bgcolor=#d0d0d0| '''Event
 * ME 564
 * ''-15 PY*
 * 1261 RC
 * Humans arrive on Dereth.
 * ME 579
 * 0 PY
 * 1276 RC
 * Olthoi Queen is defeated.
 * ''ME 591**
 * 12 PY
 * 1284 RC
 * Marae Lassel opens.
 * colspan=4| *Stated in numerous other sources. **extrapolated from 1:1 ratio of Eipothi to PY.
 * }
 * Marae Lassel opens.
 * colspan=4| *Stated in numerous other sources. **extrapolated from 1:1 ratio of Eipothi to PY.
 * }
 * }

Here we encounter a problem: the years are not progressing a steady rate between Auberean and Ispar. In the first two events, there is a 1:1 ratio between Auberean years and Ispar years. Between the 2nd and 3rd event however, the ratio changes to 1.5 Auberean year per 1 Ispar year. Later in early 2003, Turbine released The History of Auberean. In this series of articles, we are given the following information:


 * bgcolor=#d0d0d0| '''PY
 * bgcolor=#d0d0d0| '''RC
 * bgcolor=#d0d0d0| '''Event
 * -1,441 PY
 * 324 RC
 * Jojii receives his vision.
 * -869 PY
 * 704 RC
 * Alfric, Overlord of Viamont, invades Aluvia.
 * -779 PY
 * 765 RC
 * Queen Alfrega takes the throne in Aluvia.
 * -758 PY
 * 779 RC
 * King Osric takes the throne in Aluvia.
 * -540 PY
 * 924 RC
 * Gharu'n invades Roulea.
 * -358 PY
 * 1046 RC
 * Emperor Kou unites the Sho.
 * -15 PY
 * Portals to Dereth begin to open in Aluvia.
 * 0 PY
 * Olthoi Queen is defeated.
 * }
 * Emperor Kou unites the Sho.
 * -15 PY
 * Portals to Dereth begin to open in Aluvia.
 * 0 PY
 * Olthoi Queen is defeated.
 * }
 * 0 PY
 * Olthoi Queen is defeated.
 * }
 * }
 * }

Here we have a constant ratio of 1.5:1 Auberean:Ispar years.

Conclusion
Given that the "Ages of the Empyrean" article included a ratio of 1.5:1 Auberean:Ispar years for one set of dates, and that all the dates in the more recent "The History of Auberean" used this ratio, we can conclude that this is the correct ratio, and that the dates in "The History of Auberean" should be considered accurate.