Problem:

In order to calculate the difference between two time values, the earlier time must be subtracted from the later one.
However, when the later time refers to the following day (with respect to the earlier time), an error will result.
We want to create a formula that avoids these errors when calculating the difference between any two time values.

Solution:

Use the MOD function as shown in the following formula:
=MOD(B2-A2,1)

Note:
Apply hh:mm format to all cells containing the formula.