@Samantha472 You realized your mistake on the check-in day you had (accidentally) booked and now you think you should get a refund? Do you realize that the host's calendar was blocked for those days and that your mistake prevented them from getting another booking? So you think the host should be out the $ instead of you?
An Airbnb isn't like a hotel, where if a guest cancels, someone else will probably appear at the front desk looking for a room within an hour or two.
Not only did you enter the wrong dates, you apparently didn't bother to check over the booking confirmation/itinerary you would have immediately received. If you had, you would have caught the error and been able to cancel with full refund within the 48 hours.
We all make mistakes, and this was an unfortunate and expensive error and I'm sorry it happened to you, but sometimes we just need to suck it up and take responsibility for our own mistakes.