Republic Day honors the date on which the Constitution of India came into force on 26 January 1950 replacing the Government of India Act (1935) as the governing document of India.
The Constitution was passed by the Constituent Assembly of India on 26 November 1949 but was adopted on 26 January 1950 with a democratic government system, completing the country's transition toward becoming an independent republic. 26 January was selected for this purpose because it was this day in 1930 when the Declaration of Indian Independence (Purna Swaraj) was proclaimed by the Indian National Congress.
It is one of three national holidays in India, the other two being Independence Day and Gandhi Jayanti.
