Stacked Bar Chart with horizontal axis as dates

I'm using Excel Mac 2011.

I created a stacked bar chart as a Gantt chart. The vertical (category) axis is 20 Tasks entered as text. The horizontal (value) axis values are the dates spread over 2.5 years. They are in date format in the spreadsheet.

On the chart I want the horizontal axis scale to be Dates with an indication at the start of each month, i.e. J, F, M, etc. When I go to Format Axis, the horizontal axis scale is Auto (numbers) and I can’t change it to Dates.

As a work around I selected Major unit as 30 and formatted Number as Date > "M". The "months" are not spaced properly since months do not have same number of days. You will see J J M A M M etc.

I saw a similar posting on another forum but there was no fix.

Thanks for your help