24 hour time in excel

[Chris Burton]

Hi waymuggers

I have a time calculation problem I've being trying to resolve for  
the past 4 hours, and my brain now hurts a lot!.
I have two excel files filled with 9000 records from a gps in which  
the time was set to be 8 hours behind. If I add 8 hrs to those  
records with the time after midnight (eg 0:00:25) for example, starts  
the day at 8:00:25. But the records with time prior to midnight (eg  
22:15:25 ends up at 30:15:25). For the life of me I cant figure it  
out, even after doing some googling. Can someone with good brain  
cells please help me?

kindest regards

chris