How many years did the Portuguese rule Macau before it was transferred back to China?

Macau or Macao, officially the Macao Special Administrative Region of the People's Republic of China, is a special administrative region on the western side of the Pearl River estuary in southern China. Macau was formerly a colony of the Portuguese Empire after Ming China leased the territory as a trading post in 1557. Portugal governed the area in a style under Chinese sovereignty and authority until 1887 when it was given perpetual colonial rights for Macau. The colony remained under Portuguese rule until 1999 when it was transferred to China. As a special administrative region, Macau maintains separate governing and economic systems from that of mainland China.

After China first concluded arrangements on Hong Kong's future with the United Kingdom, it entered negotiations with Portugal over Macau in 1986. They were concluded with the signing of the 1987 Joint Declaration on the Question of Macau, in which Portugal agreed to transfer the colony in 1999 and China would guarantee Macau's political and economic systems for 50 years after the transfer. In the waning years of colonial rule, Macau rapidly urbanised and constructed large-scale infrastructure projects, including Macau International Airport and a new container port. Macau was transferred to China on 20 December 1999, after 442 years of Portuguese rule.