The rendezvous location where Henry and Celia have dinner is supposedly the wine-only "Vin de Vie" restaurant in Carmel when, in actuality, the glass-walled restaurant with ocean views was built on a soundstage in London using an LED backdrop. It looks remarkably like Canlis in Seattle
Kate Winslet and Idris Elba were in serious negotiations for this movie with Neil Burger directing but eventually they all dropped out. Winslet and Elba ended up playing opposite each other in The Mountain Between Us (2017).
Michelle Williams was originally cast opposite Chris Pine but dropped out after the project was stuck in development and was replaced by Thandiwe Newton. Additionally, both the actor and actress were born in 1980 and were only two weeks apart from each other. Pine was born on August 26th and Williams was born on September 9th.
Actress Newton is 8 years older than her male partner Pine, an age-gap relationship with the woman as the senior partner depicted rarely enough in Hollywood that it is worth mentioning.
Both Chris Pine and Laurence Fishburn have played roles in the DC Extended Universe (DCEU): the former as Steve Trevor in the "Wonder Woman" films, and the latter in "Batman v Superman".