Subtracting Times

how to calculate time in excel from yesterdays 13:15:00 to tadays 11:25:00.

Problem:

Finding the interval between each pair of start and end times in columns A & B. An error occurs when the end time is \"earlier\" than the start time, resulting in a negative result.

Solution:

Use the IF function as shown in the following formula to determine which of the two values is the \"earliest\", and then subtract accordingly:
=B2-A2+IF(A2>B2,1)