When Margine is talking to Jim about visiting Mexico, Jim states that he visits Zihuatanejo. That is reference to Aaron Mendelssohn's, the writer of the film, favorite movie being Shawshank Redemption, and the name of the beach village that Andy meets Red.
Kate's clock is the same style as Phil's from the movie Groundhog Day, starring Bill Murray, in which 12 Dates was inspired by.
The book 'Kate' unwraps in the opening scene, is The Lucky One, written by Nicholas Sparks in 2008. It was later turned into a film (of the same name) in 2012. Among his works are The Notebook, A Walk to Remember, and Message in a Bottle which, along with eight other books, have been adapted as feature films.