Excel calcutions using date/timestamps

[ghl]

I'm trying to write an excel formula to calculate the performance improvement
using timestamps.

Process A took 2hrs, 20 min, 9 sec expressed as 2:20:09
Process B took 1hr, 12min, 28 sec expressed as 1:12:28
Difference is calculated as a-b = 1:07:41

How do I calculate the Process B percentage improvement in processing time
using these timestamps?

 

[Gary Brown]

assume 2:20:09 is in cell A1
assume 1:12:28 is in cell B1
=(B1 - A1) / A1
and format for %
This would give -48% or a 48% decrease in time from 2:20:09 to 1:12:28.