@Chad-and-Char0 Sounds like a glitch. Happened to friend of mine as well. You'll have to contact Airbnb to get them to find out what's gone on. Make sure you get it clear with them what to do about this request- you don't want to get your response rate dinged because you didn't Approve or Decline within 24 hours. In the meantime, check your calendar, and if you see the dates past 3 months from today open, you'll have to manually block them. And message the guest back letting them know what happened.
You are sure this was request, not an Inquiry? Because guests can put in any dates they want for an Inquiry, I believe.