In the Greek Kalendar January 1, the day of the death, is observed in honour of the saint.  In the West St. Basil’s day is June 14, the traditional date of the consecration.  The martyrologies of Jerome and Bede do not contain the name.  The first mention is ascribed by the Bollandists to Usuard.  (Usuard’s martyrology was composed for Charles the Bold at Paris.)  In the tenth century a third day was consecrated in the East to the common commemoration of SS. Basil, Gregory of Nazianzus, and John Chrysostom.