Now, if you'd like to create 'Date' related Progress bars, you can follow the next steps.

Select (Due, Started, "days"), then hit "Done" when the formula looks as below.

Copy out this formula and hit 'Done' (note: the property for 'Days Between' was renamed to be 'Duration' in this example--so you'll need to either also rename your property, or just put 'Day Between' in the formula instead of 'Duration').

And voila, you now have a 'Date Progress' bar, also.

Single Database Progress Bars