"Robinsg" wrote:
Aha, I have it.
From the Paste Special menu I change the Paste option
from All to Values, Operation to Add and then OK. The
correct date is shown.
If I press Escape now the new date is correctly shown.
If I press Enter instead of Escape I get 31 shown and
a Ctrl Drop Down menu.
Somehow this differs from 2007 but that's fine as long
as it works.

Enter and Esc work the same way for me in both XL2003 and XL2007.

IIRC, Enter is a short-cut for paste after copy. (I never rely on it.)
Since the cell with 31 is still the active copy ("marching ants"), pressing
Enter will copy it to the selected cell(s).

Pressing Esc simply "cancels" the active copy; it turns off the "marching
ants".