Yes, there is. Although it is technicaly implemented as a function, it is ususally not considered a true function, but rather an operator. It is called "MINUS" (has nothing in common with MINUS "SET OPERATOR")or "SUBTRACTION" in spoken language, it's simbol is "-". It is used both in NUMBER as well as in DATE arythmetics.

To get the time difference between two dates, simply use it like this:

SELECT :date2 - :date1 FROM dual;

You'll get time difference, expressed in days.