Calculated fields

Hello Gurus,

I have two columns in my database:

Start
End
Field1 <- this is a calculated field

I have a formula in calculated field:

[End] - [Start]

the result always return 12:mm:ss tt

for example:

Start = 07/30/2014 10:00:00 PM
End = 07/31/2014 10:05:00 PM


Field1 = 12:05:00 PM

I just want to display the exact result which is:

00:05:00 PM