hi there! The exams would not have been possible if both of them were on same dates.But since they are not colliding, it is completely fine as per the rules. Yaa, it is a bit tedious for students, but it cannot be avoided until and unless any further notice comes. But i can tell you its quite possible as i myself had BITSAT on 20th May,2017 and JEE ADVANCE on 21st May,2017.