Hi Barry and Dave,
Barry's solution worked perfectly for an Excel beginner:
1) Insert "dummy" column (for example, A) next to the date column to convert (for example, B)
2) In the dummy column, first cell (or 2nd cell down if there are column headers), enter:
3) Copy the formula down the rest of the column
4) Select the entire dummy column (except the heading if there is one), and copy
5) Paste entire column over the original wrong dates in the original (A) column, Right click to paste instead of CTL-V and select Paste Special --> Values to paste the values instead of the formula, or just use Edit > Paste Special > values
Dave - thank you so much for your response, but it's too sophisticated for me. IYour solution would be oerfect if I had the time to figure out everything, but I just need a simple Excel solution right now. But thank you for your input. Someday, I may be resorting to VBA for some of these solutions.