Excel 2010 - Scatter chart needs to show data for 3 years

Hello,

I'm trying to display data for three years on a scatter chart in order to compare email open rates across years. I've managed to get all the data points displaying where they should in relation to the y-axis, but haven't figured out how to format the x-axis so they are landing correctly. I've tried formatting the x-axis different ways, but nothing seems to work.

I'd like to have the x-axis display the months February through July independent of any year, so each month is only listed one time along the x-axis.

Right now there are data points for various dates in the month of February, for example, (Feb. 14, 2011, Feb. 20, 2012, and Feb. 18, 2013), but they aren't staggered along the x-axis (they are lined up). Or a May date is lined up with a June date, etc. Spreadsheet attached.

Any suggestions are most welcome. Thank you in advance.

Regards,
Ann