I've a table with working_hours time(0), lunch_hours time(0) What I have to do is the following: If lunch_hours is greater that one hour, I have to calculate the offset Example: lounch_hour = 01:30:00 = offset = 00:30:00 Once done I've to subtract the offset from the working_hours value Example: offset = 00:30:00, working_hours = 07:30:00 = working_hours = 07:00:00 The result must be in time(0) format (hh:mm:ss) I've tried several solutions but still not working. Used DATEDIFF probably didn't used in correct way. Thanks for any help Bye!