The current calendar system adopted across Ostentia is Cariptomnian, which details approximately the last 2000 years of human endeavour. Previous systems, such as the Dityclosedean, were used prior to this and still exist in classical records
Dityclosedes and the Age System[]
Until approximately 3000 years ago, the various areas of Ostentia all used the same calender system, which had been created by the Falahnese philopher, Dityclosedes. It was universally accepted by the populace and all religious leaders. The system, dubbed the Age System by researchers, works on the principle that the entire history of the world could be split into "Ages".
The first of these was the Age of Origin, which Dityclosedes asserted was when the World and humans were created, and the time after. The view of many scholars is that Dityclosedes had no positive feelings for this era, and his statement that "[p]rimitive humans were at no point capable of rationalised thought" certainly backs up this assertion.
The Age of Truth succeeded it upon the creation (or, as some religions chose to state, discovery) of the Age System. Dityclosedes also made predictions about the following ages. Dityclosedes predicted that the Age of Mercy would follow Truth after what scholars have calculated as roughly 700 years (the Age System's demarcation of dates had no link to natural occurences, so scholars' interpretations vary between 500 and 2000 years.)
The Eronam Empire's invasion[]
Approximately 750 years after Dityclosedes' predictions, The Eronam Empire began to conquer Ostentia. The Empire's occupation was thought to be the beginning of the Age of Mercy by believers in Dityclosedes and, with their retreat, the Age of Judgement began. This age is considered under the Dityclosedean system to be a trial of their religious and moral belief.
Historians and some Dityclosedean rebels believe another Age has just begun, or is about to do so. This is the last recorded Age in what remains of Dityclosedes' documents. Orthodox followers of Dityclosedes believe that the Age of Judgement shall not end until an apocalypse, taking the idea of the Age of Knowledge as a symbol of a pleasant afterlife.
The system went out of use with The Eronam Empire's arrival, however, as they brought their own system with them. Nonetheless, very little documentary evidence of this system in detail exists, although archaeologists are currently excavating sites in Eronam. Historians have taken this lack of evidence to suggest that it was highly unpopular in Ostentia, along with the ingress of the Eronam Empire.
Cariptomni and the BC/AD system[]
2000 years ago, another Falahnese philosopher, Cariptomni, took this Eronamese system and made his own system, widely considered superior. Though this too proved unpopular to begin with, as it was adapted from the Eronamese system, it was far more useful than the Age System and quickly spread, even to other parts of the Empire. The system started with the year it was devised as 0, and each year onwards would add 1 to the number of the year. This system is still used today. BC and AD sufffixes are used to designate whether the year is before this 0 or after. AD stands for After Dityclosedes, signifying the end to his system; historians have often found the lack of references to the Eronamese as a clear sign of its unpopularity. BC stands for Before Cariptomni. For example, 2007 AD means 2007 years after Cariptomni introduced his system.