Hi 222dfb,
Currently we don't offer a calendar-style date picker to select the due date. Clicking on the calendar icon next to the due date will open the Due field for editing, but you will need to type the due date. You can find a list of acceptable date formats here.

If this isn't the behavior you're seeing, would you be able to contact us so we can take a closer look?

Thanks!

You can see the 148 other posts from folks who think there should be a date picker here: http://www.rememberthemilk.com/forums/ideas/4317/