A1 = Time 1, B1 = Time 2, C1 = Time Difference
If A1=B1 then C1= "On Time"
If A1B1 then C1 = "Late By h:mm"
If A1<B1 then C1 = "Early By h:mm"
Also A1 may be a PM time and B1 may be an AM time

Examples:
A1=10:00 PM, B1=10:00 PM, C1=On Time
A1=9:30 PM, B1=10:00 PM, C1=Early By 00:30
A1=12:15 AM, B1=10:00 PM, C1=Late By 2:15

This is killing me. Thank you in advance.