▁end ors ed ▁the ▁independent ▁procedure ▁that ▁had ▁been ▁in ▁use ▁for ▁some ▁time ▁at ▁Rome ▁and ▁Alexand ria . ▁E aster ▁was ▁hence forward ▁to ▁be ▁a ▁Sunday ▁in ▁a ▁lun ar ▁month ▁chosen ▁according ▁to ▁Christian ▁criteria — in ▁effect , ▁a ▁Christian ▁N isan — not ▁in ▁the ▁month ▁of ▁N isan ▁as ▁defined ▁by ▁Jews . ▁Those ▁who ▁argued ▁for ▁continued ▁reli ance ▁on ▁the ▁Jewish ▁calendar ▁( called ▁" pro top as ch ites " ▁by ▁later ▁histor ians ) ▁were ▁ur ged ▁to ▁come ▁around ▁to ▁the ▁majority ▁position . ▁That ▁they ▁did ▁not ▁all ▁immediately ▁do ▁so ▁is ▁revealed ▁by ▁the ▁existence ▁of ▁ser m ons , ▁can ons , ▁and ▁tract s ▁written ▁against ▁the ▁pro top as ch ite ▁practice ▁in ▁the ▁later ▁ 4 th ▁century . ▁ ▁These ▁two ▁rules , ▁independence ▁of ▁the ▁Jewish ▁calendar ▁and ▁world wide ▁uniform ity , ▁were ▁the ▁only ▁rules ▁for ▁E aster ▁explicitly ▁laid ▁down ▁by ▁the ▁Council . ▁No ▁details ▁for ▁the ▁computation ▁were ▁specified ; ▁these ▁were ▁worked ▁out ▁in ▁practice , ▁a ▁process ▁that ▁took ▁centuries ▁and ▁generated ▁a ▁number ▁of ▁controvers ies ▁( see ▁also ▁Comput us ▁and ▁Reform ▁of ▁the ▁date ▁of ▁E aster .) ▁In ▁particular , ▁the ▁Council ▁did ▁not ▁seem ▁to ▁dec ree ▁that ▁E aster ▁must ▁fall ▁on ▁Sunday . ▁ ▁Nor ▁did ▁the ▁Council ▁dec ree ▁that ▁E aster ▁must ▁never ▁co inci de ▁with ▁N isan ▁ 1 4 ▁( the ▁first ▁Day ▁of