If you want to show a number of hours beyond 24, [hh]:mm will show them.
Formatting as hh:mm (without the square brackets) would not.

If you want to return the number of hours as a decimal, then use
=(B1-A1)*24, and format as general or number, not as time.
--
David Biddulph

"Igor" wrote in message
...
Thank you I tried, it returns only hours and minutes, however, days are
missed in the return

"Mike H" wrote:

Hi,

with the eralier date/time in A1 and the later in b1 try

=B1-A1

Format the cell as [hh]:mm

Mike

"Igor" wrote:

I need a formula to calculate number of hours between data and time set
in
the cell by function NOW() and a set date in the same format:

Example:

NOW() - return 29/07/2009 16:06:00
set date - 07/08/2009 06:00:00
result to be difference between the dates presented in hours