Atlian years are based off of the start of the Cirilian Era, when the three major Atheran civilizations agreed on a succinct calendar:
(One Atlian year is equal to one month in real time.)
The First Era: 200 BCE - 0 BCE
The Cirilian Era: 1 ACE - 250 ACE
The Era of Revolution: 251 ACE - 400 ACE
The Era of the Obelisk: 401 ACE - Present
Each Atlian year consists of four seasons:
Specific dates are written as: (Day of Season, Year)
I.e. 5th of Evermoon, 415 ACE