The year is set by the first theatrical release date, if there is one entered. Much of the theatrical release dates for this film are in January 2020, so the data is correct.

Think this was 2019 here until very recently. It just changed on Letterboxd to 2020. The film had its world premiere as a VIP special screening at Curzon Mayfair on December 3, 2019m but as far as I can understand, TMDB does not consider that a proper premiere, as therefore lists it as a 2020 movie, even if it's a 2019 release on IMDB, Google, Rotten Tomatoes, Wikipedia. It does say 2020 on the blu-ray cover.