How to click in box with elements on it

Hi,
Any one can answer this?

This is a calendar and I want to click in side of this box. This box is date of each month.
The problem is that some events are already on that box and there is no space left to click on it.
I have to double click in box but when I give xpath and click on it, it clicks on event rather than inside the box.
I can click manually in white space between events but how could I click with selenium

Any solution please.

Cheers,
Waqar Ali