Why the ordering of the quantifiers matters here? $\newcommand{\fool}{\operatorname{fool}}$I want to transfer the statement 

You can fool all the people some of the time

into predicate logic.
Now I am using fool(X,T) to mean that I fool person X at time T.
Now I know that the correct form is $\exists T\  \forall X\  \fool(X,T)$.
But I want to understand why is it not correct if we change the ordering of the quantifiers to $\forall X\ \exists T\ \fool(X,T)$.
The first one is saying there exists a time that I can fool all people right ?
Ans the second one is saying for all the people out there, There exists a time that I can fool you , right ?
What is the difference ??
What makes the first once correct but not the second.

The difference is that in the second case, different people are fooled at different times.  Suppose I can fool all Christians on even-numbered days and all Muslims on odd-numbered days, and everyone is either a Christian or a Muslim.  That doesn't mean there is any day on which I can fool all of the people.
