Copy/paste only valid cells Excel

Hello.

I have a column in Excel where some of the dates are aligned to the left (they need to be on the right). I fixed this by duplicating this column and using DATEVALUE on all the cells. This fixed the wrong cells, but gives an error on the good cells though.

So how can I copy the now-fixed cells to my original column without losing the other good cells.
I've added an example image with dummy data to clear things up. (Don't worry about the red mark-up, that doesn't matter)

Hope you can help.
Thanks in advance!
Nicolas


Knipsel.PNG