I think you're worrying about this preemptively (I do the same thing all the time). You have no idea yet whether or not you'll be ready by then anyway. Besides, I feel like you tend to meet someone when you're supposed to meet someone, whether that's in two months or two years I can't say. Don't force yourself into dating…which sort of sounds like what you want to do from your post. Maybe that's why you're getting the reactions you're getting? People see you're clearly not ready yet and yet you're talking about dating already.

To answer your last question, it's however long you need. If a date tries to dictate to you how you should feel and how you should live your life (as in saying "you should wait"), then that's probably not someone you want to get involved with in the first place.