definiens: shall mean the period from January 1 of a Calenda r Year until December 31 of the same Calendar Year during the Fu ll Research Program Term ; provided, however, that ( a ) the Research Program Year 1 began on the Effective Date and shall be deemed to have ended on December 31, 2015, ( b ) the final Rese arch Program Year of the Research Program Term ( which will be : ( i ) Research Program Year 6 if there is no First Extension Period, ( ii ) Research Program Year 8 if there is a First Extension Period but no Second Extension Period, and ( iii ) Research Program Year 10 if there is both a F irst Extension Period and a Second Extension Period ) shall begin on January 1 of the applicable Calendar Year and end on March 31 of such Calendar Year, ( c ) the Research Program Year that c orresponds to Tail Year 1 ( if any ) shall begin on April 1 of the applicable Calendar Year and end on December 31 of the same Calendar Year and ( d ) the Research Program Year that corresponds to T ail Year 4 ( if any ) shall begin on January 1 of the applicable Calendar Year and end on March 31 of such Calendar Year