A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data
Hi,
That entry is most likely not a proper date - looks like the day and month positions have been interchanged. Select the range of dates (appearing in a single column) and go to Data > Text To Columns. On the third screen, select Date > MDY > Finish. This should change the data type of the entries in that column to Dates. Now you may format the entries in this column.