The Kronite Calendar

The Kronite Calendar was originally formulated by the scholars of the Arcane Isles and it is regarded as being a divinely inspired gift from the god of time Kroni, after whom it is named. Since its inception it has been adopted across the entire of Kelbonnar's Planes, with creatures from the Hellish Plane right the way up to the Celestial Plane using it to keep track of the passage of years. 
In terms of the tracking of years, the calendar has been split into two eras, the Divine Peace and the Divine War, with the current year being 574 of the Divine War.
Whilst the 10 months of the calendar have been named, the days remain nameless, with individual days being referred to simply as 'the 4th day of ...' or 'the 2nd day of the 3rd week of ...'.