Why does the woman suggest that the man change his reservation date?

W: Good afternoon, Pingpang Hotel. May I help you?
M: Yes, I’d like to make a reservation, please.
W: Certainly, sir. Which date would that be?
M: From the 27th until the 29th of June.
W: Could you hold on a moment, please? I’ll check our reservation record... Thank you for waiting, sir. I’m afraid our hotel is fully booked on June 27th. Is it possible for you to change your reservation date? How about from the 28th to the 30th of June?
M: No, that’s impossible. That date is my anniversary. I want to give my wife a surprise and celebrate it at the hotel.
W: Well, we might have cancellations. Could you call us again closer to the date?
M: Sure, but if you have any cancellations, could you let me know as soon as possible?
W: I’m very sorry, sir. But we are unable to do that. We would appreciate it very much if you could call us instead.
M: Well, are you kidding? If that’s the case...
W: We’re very sorry, sir. We hope you understand.
M: OK, I know what you mean. Thank you for nothing.