definiens: means the respective periods of three ( 3 ) consecutive calendar months ending on March 31, June 30,September 30 and December 31 of each calendar year, provided that ( a ) the ﬁrst Calendar Quarter of the Term shall begin on the Eﬀective Dateand end on the first to occur of March 31, June 30, September 30 or December 31 thereafter and the last Calendar Quarter of the Term shall endon the last day of the Term and ( b ) the ﬁrst Calendar Quarter of a Royalty Term for a Licensed Product in a country shall begin on the FirstCommercial Sale of a Licensed Product in such country and end on the ﬁrst to occur of March 31, June 30, September 30 or December 31thereafter and the last Calendar Quarter of a Royalty Term shall end on the last day of such Royalty Term