The timeline of the film occurs over the course of a decade. Harry and Sally first meet when they share a drive from Chicago to New York after graduating from college. The story jumps ahead five years and they meet on an airplane, and then it advances another five years in the future when they meet once again. There is an element of fate that plays throughout this film that becomes a motto for the audience who sees clearly that "maybe you two should get together." Reiner's film, written by Nora Ephron, questions whether men and woman can actually be friends or if all male/female relationships end in either relationships or sex.
The evolution of the characters is interesting in that Harry is so strong minded that he insists that men and woman cannot be friends initially and then 5 years later rejects that he's said this. Sally is strong minded as well but generous in giving Harry the space to speak out his never ending beliefs on relationships that seem tormented with gloom. When Harry and Sally get together at the end of the picture it's because Harry has finally let go of the "idea" of what a relationship must be, and allowed for what has happening right in front of him to be the reality that he must live in. And his ideas about women, which up until this point are absolutes--every woman is this or that and believes or needs this or that--there is nothing in between. Sally shows him the reality that every woman is not what Harry believes it is.
Sally remaining firm in her beliefs about the reality of the differences of a man and woman from person to person eventually reveals itself to Harry after he sleeps with Sally and leaves her in distress. The film is about a man actually becoming a human being rather than a social dictate. Once he lets go of these absolutes he can tell Sally how he feels and actually begin to have a real relationship with her rather than trying to constantly dictate what she must believe about herself and their relationship.
