It's Excel 2010 (I should really update my profile).

As you can see from the screen shot, the row of dates are set to Date format:



^ I right clicked on cell B1 and selected Cell Formatting.

I followed gebobs suggestion but that seemed to have no effect.

Will cells that are formatted for Date recognize their format as date if they're not entered right in the first place? Because the dates you see are exactly how I entered them. Perhaps it needs a specific format like 13-02-2017?