User blog comment:Shaldemar/New World Calendar/@comment-70.190.216.70-20160622012344

There is really no set calendar system within D&D, unless they changed that after the 3rd Editon rules. However TSR games (original publisher which was bought by Wizards of the Coast who in turn were bought by Hasbro), had several World Settings. I still own pretty much everything that TSR published from the late 70's to the late 80's and I don't remember them specifying a calendar in any of them (Greyhawk, Dragonlance and Forgotten Realms).