The Varandian Calendar

Created in Reisenhoff in 363 Godsmarch and named after the scholar, Erik Varand, who invented the dating system in order to appropriately categorize and chronologically align the events in his work, the Varandian Calendar is currently the most popular form of calendar in northern Estlund. A single year in the Varandian system consist of 365 days divided among twelve months of either 30 or 31 days each. 
Currently, most scholars consider it the most accurate calendar to have been used so far, having required no corrections during its four centuries of usage. During its development, Varand calculated the starting date based on historical records of the alignment of the stars during the Godsmarch and extrapolated both forwards and back to several major events before and after that which also had recorded alignments of celestial bodies.