Why does the man talk to the woman?

M: Are you doing anything on Monday?
W: Nothing special. Why? What’s on Monday?
M: I thought I’d have a party.
W: Nice. What time?
M: Evening. Nine o’clock. That sort of time.
W: What’s the celebration?
M. Well, it’s my birthday on Saturday, but I’ll be away the whole weekend.
W: Friday’s a nice day to have a party, isn’t it?
M: Well, I was going to have it on Friday, but Friday has rather good TV programs.
W: I know what you mean.