Gateway of India illuminated with Tricolour lights

© Sourabh Kumar/500px/Getty Image

India's 73rd Republic Day. Republic Day

India is celebrating its 73rd Republic Day - the day when the Constitution of India came into effect, replacing the Government of India Act (1935) as the governing document of India and thus, turning the nation into a newly formed republic.

The day also marks the transition of India from an autonomous Commonwealth realm with the British Monarch as nominal head of the Indian Dominion, to a fully sovereign republic in the Commonwealth of Nations with the President of India as the nominal head of the Indian Union.

To mark the occasion, several important buildings across the country, like the Gateway of India in Mumbai, lit up in the colours of the national flag.