Between Dates Calendar Math

I have depended on this app for several years. I use it to advise me of things that must been done on exact dates in the future. The developer is extremely responsive and accommodating. Thank you !!

Taking a medicine BID for 15 days means you should have 1 day and 7 hours left. need hours and seconds.

I don't really like the layout . Picking a date and having to copy to start or end is too much work for me. I just wanted a simple date difference. Maybe 2 spinning wheel top n bottom n result in the middle? And a subtract box next to result? I think most ppl would prefer something nice simple n efficient. I will keep this app since I need something like this, until probably the next update.