Definitely, Maybe

25: Will hands Summer her diary and he admits he read it. Hampton, her beau, sleeps next to her. Will compliments Summer and in the hallway Summer kisses him. She suggests he call her for dinner or something. The birth of something new.

45: Will goes to one knee to ask Emily to marry him. Emily says no and tells Will she slept with his roommate. She tells him "I'm letting you go." They go their separate ways. Now that I'm aware.

60 and -45: Hampton is in the hospital, Summer is beside him. Will is in the hallway. Hampton wants to know if Summer loves Will. Summer won't tell him and calls him a drama queen. Later, Will is at an important political event at the Grand Hyatt. He handles pressure well as turbulence among colleagues intensifies. There's no going back now and Discovery.

-25: Will walks a bit and finds the Jane Eyre book April's father dedicated to her. He buys it and goes to her apartment to give it to her but discovers Kevin is her new live-in beau. Will decides to keep the book and leaves without saying good-bye. Eventually he'll give April the book and the movie ends with them getting back together. The final turning point.