The history of Hong Kong is intertwined with British colonialism and China’s Hong Kong policies. This history offers unique and important lessons on the rise and fall of Hong Kong’s constitutional order. In accordance with the 1984 Sino-British Joint Declaration, China declares 12 basic policies regarding Hong Kong and has translated these into the 1990 Hong Kong Basic Law. It is generally held that “One Country, Two Systems” will be the main constitutional architecture of Hong Kong for 50 years, and it will remain basically unchanged even after 2047. However, there are obvious difficulties and enormous differences on the interpretation of Article 5 of the Hong Kong Basic Law concerning the true meaning of “unchanged for 50 years.” Recent years have witnessed the great need for deciphering the time-code of the Basic Law because the question of 2047 draws closer and closer to the central stage for the determination of Hong Kong’s constitutional future. This Article aims to provide legal analysis on Article 5 of Hong Kong Basic Law and the constitutional fate of Hong Kong toward 2047. It distinguishes all sorts of Article 5 interpretations into three broad categories: “Unchanged for 50 years” as international promise, “unchanged for 50 years” as political commitment, and “unchanged for 50 years” as constitutional obligation. Different approaches have been utilized for various constitutional interpretations. But all in all, the constitutional puzzles regarding “unchanged for 50 years” must be addressed within the framework of the temporality of the Basic Law in a fast-paced world. In order to maintain the constitutional stability and endurance, to secure the unamendability of “One Country, Two Systems” in 2047 will be the best blessing for Hong Kong in every possible way.