I want to set an IF function based on date.

The premise is that bonus pay is paid only if an employee works up to or
after a specific date. If the end date of the employee is before DATEX, then
do the calcuation, if not, the calculation is irrelevant. It looks like this:
=IF(B3DATE,(T5*U8)/12,"0")
Except the function doesn't use the date in the way I intend. Is there a
different function I should be using and how?