Ok so when I was gardening my Dandelion needed 3 hours and 30 minutes before I could harvest them. I waited for a long time and it still says that! My Pink Dandelion did that also. It needed 7 hours and something minutes and again I waited long, and I checked up on it, and it still says 7 hours and something minutes! How is this possible? :?
I don't think having pests or needs stops the plants from advancing (although it does seem to slow them down) - but, of course, you can't harvest anything that has pests or needs.
The time is realtime, of course. You'd have to wait at least 3 hours and 30 minutes before you could harvest the Dandelion - longer if they had Needs or any pests on them.