When doing a Show Posts Special, can you please remove the check to make sure that the From date is less than the To date. In both the Date Range and Calendar options.
When entering this information as a Date Range, it is natural to want to load the headers from 100 days to 110 days. Newsbin requires you to enter this information as from 110 days to 100 days.
There is no real reason to not swap these numbers if there are specified in the 'wrong' order. They are specifying a range, and that range is valid regardless of which box or calendar contains the 'lesser' date.