Hovering Over the data point shows different X-Axis
 

I have an area chart with several data points. The chart looks correct, but
if I hover over one of the data points the X-axis that it indicates is one
off the correct X axis. If I only select data for 2 years (24 points) it is
okay. As soon as I add the 25th, the hover over shows the following month
(the data is still correct).

Is this a limitation in Excel or has anyone else come across this?