I have a spreadsheet with 2 date columns. Column H and column F.

1 column shows the last date an review was made and the other column
shows the date the next review is due.

I am using the following formula in column F to update the next review
date, ie =H1+7, which advances the date in column F by 7 days.

My problem is that I am making new enttries down the columns and when
I try to format column F all the down to save time entering the above
formula, where there are no entries in column H then I get 07/01/1900
in each cell. How can I stop 07/01/1900 being displayed and simply
have a blank cell until I make an entry?

Thanks

(Excel 97 and 2000.)