Undo Calendar Changes?

I missed day 41 on my FB Fit program last week, but when I went to reschedule I accidentally selected day 40 and rescheduled for today. Well, I am actually on day 41 today but the calendar won't let me move day 41 onto today's date because day 40 is already scheduled there. Is there any way to undo the day 40 reschedule so I can correctly reschedule day 41? My calendar will be off for a while now and while it's not a deal breaker it is annoying.

I completed day 40 two days ago but since it's in the past there seems to be no way to tell the calendar that yes, I did complete that workout 2 days into the past. Can we be allowed to schedule 2 workouts on the same day on the calendar? Or even just an "undo changes" button or would be beneficial. I'm thinking I could probably just delete the whole thing and attempt to re-enter the program and reschedule it, but then I would lose all the data and "completes" that have populated my calendar. I'm hoping the developers were forward thinking enough to come up with a logical solution that doesn't involve me firebombing my program out of existence and starting from scratch. (fingers crossed...)

If anyone has any tech know-how that could help me out I would greatly appreciate the advice.