Although the Constitution of India was adopted by the Constituent Assembly on the 26th November, 1949, it came into full force only on the 26th January, 1950, on which day India became a Republic (‘Sovereign Democratic Republic’ as per the Constitution). Some parts of the Constitution, like Articles 5 to 9 dealing with citizenship, had come into effect immediately on adoption.The Constitution of India replaced Government of India Act, 1935, enacted by British Parliament, as the governing document of India.
The date 26th January was chosen by the Constituent Assembly to commemorate the 26th January, 1930 on which day the ‘Purna Swaraj’ (complete independence) Resolution was adopted at the Lahore session of Indian National Congress (the original nationalist, all-embracing organization, the Indian National Congress, not the present truncated, emaciated and grossly politicised and totally transformed outfit, the original nationalist party having been split and re-split by Indira Gandhi in 1969 and again in 1978 to suit her personal aspirations, whose official name since 1978, has been ‘Indian National Congress – I’, the ‘I’ standing for ‘Indira’).
On the 26th January, 1950, the first President of India, Dr. Rajendra Prasad, participated in the first Republic Day Parade, riding on a traditional horse-drawn carriage. Since then, morals have deteriorated and security has become a high risk affair and, understandably, the open and risky horse-drawn carriage has given way to a high security limousine used by present-day Presidents.
Here is a view of the first Republic Day parade of India:
On Republic Day, I had been invited by the school in my village where I had studied as a child, to unfurl the National Flag. In the meeting that followed, I asked the students the difference between Independence Day and Republic Day. No student could answer satisfactorily. I explained to them that Independence Day is celebrated to commemorate India's independence on the 15th August, 1947, when India became free from British Rule and new Government headed by Prime Minister Jawaharlal Nehru took office. However India continued to be a Dominion and the British King continued to be India's formal Head of State. The Constitution of India providing for a President as the Head of State, came into full force on the 26th January, 1950 and Dr. Rajendra Prasad was sworn in as the first President of India. On that day, the British monarch ceased to be India's Head of State.
A country is a Republic where one of its own citizens is the Head of State. Australia and Canada are independent States but they continue to be British Dominions and the British Monarch continues to be their formal Head of State. Lord Mountbatten and Chakrabarti Rajagopalachari, appointed by the British Monarch, were the last 2 Governors General of India. At present, citizens of British Dominions are appointed as their Governors General and represent the British Monarch on formal occasions.
Fittingly, on the Indian Independence Day on the 15th August, Prime Minister of India as the head of Government of India, unfurls the National Flag. And on the Republic Day, the National Flag is unfurled by the President, the Head of State.
India has an Independence Day and a Republic Day but U S A has only Independence Day celebrated on the 4th of July, to commemorate the Declaration of Independence on the 4th of July, 1776. That day itself U S A had become a Republic with a President as its Head of State. It severed all its governance-connections with its British rulers on that day.