Subtract the earlier value from the later one and then use Format -- Custom
format:
[h]:mm:ss
For example with 04/12/10 10:23 AM in A1 and 04/15/10 15:18 in B1 then
=B1-A1
and with the custom formatting applied will display 76:55:00, which is 76
hours and 55 minutes.


"Rama Chandra" wrote:

i need to calculate the exact number of hours between two different dates and
times, e.x. 04/12/10 10:23 AM and 04/15/10 15:18.