If your calendar/date picker ever looks like this:
The dates are wrong and Saturdays are blank
There is actually a reason why and a straightforward way to fix it.
This happens when your browser's zoom level is set below the normal 100%. If you adjust your zoom level to be 100% the calendar will correct itself.
You can do this in most browsers by holding the Ctrl button and scrolling up with your mouse wheel.
Otherwise, here are links to do it in each web browser: