answer: #Person2# play a trick on #Person1# as it's April Fools' Day, which reminds #Person1# of his wife's birthday. #Person1# tells #Person2# his wife is Chinese so she celebrates her birthday according to the lunar calendar.
documents: #Person1#: I need to go to the bank.
  #Person2#: But they're all close today?
  #Person1#: Closed? Are you kidding? What is it? Some kind of holiday today?
  #Person2#: Have you already forgotten what's the date today?
  #Person1#: Oh, it's the first of April. April Fools' Day.
  #Person2#: You forgot all about it, didn't you?
  #Person1#: Sort of. But it has reminded me of at least one thing I need to remember.
  #Person2#: What's that?
  #Person1#: Tomorrow is my wife's birthday.
  #Person2#: Better not forget that. It's pretty strange that your wife's birthday changes every year. Why is that?
  #Person1#: My wife is Chinese. She celebrates her birthday according to the lunar calendar.
  #Person2#: Ah, I got it.
  #Person1#: It's so different from our culture. I guess that makes life interesting to have different cultures come together.