Martin Luther King Jr. Day (officially Birthday of Martin Luther King, Jr., and sometimes referred to as MLK Day) is a federal holiday in the United States marking the birthday of Martin Luther King Jr. It is observed on the third Monday of January each year. Born in 1929, King's actual birthday is January 15 (which in 1929 fell on a Tuesday). The holiday is similar to holidays set under the Uniform Monday Holiday Act. The earliest Monday for this holiday is January 15 and the latest is January 21.