Ontology as a knowledge representation have contributed in providing the platform for sharing the common ideas and understanding among the members of similar domain. Ontology has a tree structure to ease the presentation of information for the users. This paper presents the building of Dates ontology by using the OASys approaches. The Dates ontology is focusing on the Dates' attributes, the developing stages, defect and diseases of dates, health benefits, its compositions, and the Dates chain of operation. Formation of this Dates ontology can be used to answer user queries, integrate data to other applications as well as expand the ontology. � 2016 IEEE.