Just because they are now formatted as dates doesn't mean that they
aren't text values. If you change the number format, does their
appearance change?

If not then you do still have text values in the cells.
You can convert them to numerical values in a variety of ways.
Since there are only 4 it's probably simplest to do F2, Enter in each
of the cells.

Bill Manville
MVP - Microsoft Excel, Oxford, England
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