Following the 1974 Carnation Revolution, Portugal formally relinquished Macau as an overseas province and acknowledged it as a "Chinese territory under Portuguese administration". 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 urbanized and constructed large-scale infrastructure projects, including the Macau International Airport and a new container port. Macau was transferred to China on 20 December 1999, after 442 years of Portuguese rule.