Republic Day is celebrated on 26 January. It is an important national holiday in India that commemorates the day when the Constitution of India came into effect in 1950, replacing the Government of India Act (1935) as the governing document of India. This historic event marked the transition of India from a British Dominion to a republic, making it a sovereign, democratic, and secular nation.

Below are the reasons why Republic Day is celebrated on 26 January:

1. Historical Significance:
- On 26 January 1930, the Indian National Congress declared the demand for complete independence from British rule, which was known as the "Purna Swaraj" or "Complete Independence" declaration.
- This declaration marked the beginning of the independence movement in India and set the goal for achieving full self-rule.
- To honor this significant event in the freedom struggle, 26 January was chosen as the date for the adoption of the Constitution and the establishment of the Republic of India.

2. Adoption of the Constitution:
- After gaining independence from British rule on 15 August 1947, India functioned as a Dominion under the Government of India Act.
- The drafting of the Constitution began in 1946 and took almost three years to complete.
- The Constituent Assembly of India, under the leadership of Dr. B.R. Ambedkar, finalized the Constitution on 26 November 1949.
- However, it was officially adopted and enacted on 26 January 1950, making India a republic and providing a framework for the governance of the country.

3. Symbolic Importance:
- Celebrating Republic Day on 26 January holds symbolism and reflects the values and aspirations of the Indian nation.
- It signifies the triumph of the Indian people in their long struggle for freedom and self-governance.
- The day is a reminder of the sacrifices made by the freedom fighters and the vision they had for a united and independent India.
- It also reinforces the principles of democracy, equality, justice, and secularism enshrined in the Constitution.

In conclusion, Republic Day is celebrated on 26 January to commemorate the adoption of the Constitution of India, which established India as a sovereign republic. The date holds historical significance as it marks the "Purna Swaraj" declaration and symbolizes the Indian people's journey towards independence and self-rule.