WHO said we have to wish on the day before the Exam ????

Since this week is the CIMA exam week, as a habit I wish all the freinds I know who are sitting for the exam. I am used to wishing them on the Sunday of the week where the exams starts the following Tuesday. So as usual did the same. (Sent Text messages to them) I get the replies,

Friend A - "Thanks !! Exam on Tuesday...."
Friend B - "Thanks !! Exam on Thursday...."
Friend C - "Hehe 2 more days to go !! Thanks.... "
Friend D - "Thanks !! But it is on Wednesday...." Even my cousin replied in the same manner.

Wots wrong with the wishes being a few days early ??

Who the hell said we have to wish on the day before the Exam ??.............