What does the title "2046" refer to in Wong Kar-Wai's 2004 film?

Explanation

Wong Kar-wai is one of the most famous Asian film directors. He was born in Shanghai in 1956 but moved to Hong Kong at an early age. His films have a strong autobiographical slant and often feature Hong Kong. Highlights of his career include the "Hong Kong"-trilogy "Days of Being Wild", "In The Mood For Love" and "2046". 2046 refers to the year where Hong Kong becomes completely absorbed by China after several decades of British and semi-autonomous rule. Wong Kar-wai is a very visual director, and his idols in Western film making include not least Ingmar Bergman, but also Danny Boyle.