A's brithday is April 30th, and his sister (B)'s birthday is April 29th (of a different year). One day, he calls her and the first thing they say to each other is "Happy Birthday", and both's wishes are right and on time. How is this possible?
B is 3 years younger than A. B also passed a major milestone on that day.
True story BTW, as of ~4 hours ago.