Day changes at 7:00 am?

Hi all!

How to make excel 2003 think that that day changes not in the midnight, but 7:00 am?
Thanks!

P.S. I don`t want to adjust my pc clock.

In what context?

Where I am working we run 4 on 4 of shift system. One shift is 12 hours and it starts at 07:00. This is the point, where the date changes. In my project I have to do some time calculations (durations beetween tasks). But it is messed up with ########## (negative times or dates). I'm sure they not negative. Its just the system my company runs. So, I have to collate some data from paperwork and enter to my project. And if I find one task finished 20th May 22:30 and another started the same day 02:30 I want duration 4 hours, not ###########. Any ideas?

If you actually have times with dates then the date change shouldn't be relevant. If A2 has 20-May-2010 22:30 and B2 has 21-May-2010 02:30 then just subtract one form the other, i.e.

=B2-A2

and format result cell as [h]:mm

No. Date is kept separately from times. I have only one date and two different times

Spot on! Thanks!