Provisional timetables go out on 3 April. Check yours the day it arrives. A clash means two examinations at the same time on the same day. Two examinations on the same day at different times is not a clash and will not be changed, however unwelcome it is. Report a genuine clash through the student portal within five working days. After that the timetable is fixed and the only remedy is to sit one paper under supervision at a later time, which is more disruptive for you than an early report would have been. Do not contact your department. Departments cannot move examinations.