I have a cell set up as format

dd/mm/yyyy hh:mm:ss

and the contents are 01/01/1995 00:00:00

In the cell below I put 01/01/1995 01:00:00

then fill the cells for a few hundred. After about 200 cells the value shows
as

09/01/1995 10:00:01 - in other words the increment being added for each cell
is slightly greater than the desired one hour. I assume this is a lack of
precision in the cell value. Is there a way of changing this?

I am using Excel 2007.

Grateful for advice.