How old?
What age are Steve Martin's and Diane Keaton's characters supposed to be?
You realize the sun doesn't go down, it's just an allusion of the world spinning round.
Nina was supposed to be 46 and George is 47. His birthday is September 18, 1946 and the sequel takes place two years after the first one--which is what the characters state.
http://www.fanfiction.net/s/5831281/1/