Anyone know how to delete days from the calendar?

I've started my diet over today (8/9), but the calendar does not allow you to delete old information from the calendar. Today is 8/9, I had started entering information for 8/6, but screwed up. I know want to delete that day from the calendar. I figured out how to delete food and exercise from a day, but it still uses that day in averaging data for the month.

I have the same problem. I can't delete old information that I did twice.