ToDoNow: How to include a calculation of due-dates?

Hi & sorry for my late reply.
Unexpected other things came on my way…
And after Thomas reply “cannot help … datepicker in ToDoNow doesn’t work properly…” I looked around and found Pickaday (https://kookma.github.io/TW-Pikaday/) with a ToDo-List, which also almost fits my needs.

I think, the best is now to open another thread with my questions for that? Should I delete this thread?

Thanks and sorry to Tones & Thomas,
Noushka