Plotting Dates vs. Dates

I'm trying to create a graph in Excel that plots Dates on both X and Y axis. When I do this, I also want to be able to format the axis to my liking. MS Excel allows me to format the X-axis with a scale resembling dates (i.e., put the units in days, weeks, months, etc.). BUT, it does not allow me to format the Y-axis in a similar manner. Even though the data being graphed and the Y-Axis are formatted as dates, it still wants the scale of the Y-axis to be number-like. I want the scale of the Y-Axis to be date-like. How can I do this.

By the way, please don't ask me why I'm needing to plot Dates vs. Dates. I just do!!!