Both dramas deal with time travel. While Tomorrow with You goes back and forth from present day to the future and is centered around the romance between the ML and FL, 365:Repeat the year goes back 1 year into the past and centers around a group of people, that traveled back in time. Both dramas make you question what is going to happen next.
Yoo So Joon is the successful CEO of a real estate company who has the ability to time travel when he takes the subway. Going back and forth in time, he sees his future self living a life of torment and unhappiness. To try to offset his doomed future, he decides to marry Song Ma Rin, a cheery photographer, even though he does not love her. Can Ma Rin help So Joon change his unhappy future