The Koronikon system, used in medieval Georgian manuscripts, records years in 532-year cycles beginning at a base year of 780 AD. While scholars have long converted Koronikon dates to AD years using tables and colophons, no explicit mathematical formulation of this procedure has been published. This paper presents a closed-form formula that performs the conversion systematically, incorporating a historical minimum date constraint via a ceiling function to resolve cycle ambiguity. The formula is validated against six manuscript and numismatic test cases spanning the 10th to 18th centuries, yielding zero error in all cases.