Monday marks India’s 66th Republic Day, celebrating the effective date of the South Asian country’s new constitution in the wake of 200 years of British colonial rule. Today, India is the largest democracy in the world. “Constitution is not a mere lawyers document, it is a vehicle of life, and its spirit is always the spirit of age,” B.R. Ambedkar, who drafted the Constitution of India, memorably said in a quotation cited by Goodreads.

With U.S. President Barack Obama in attendence this year for the first time, there has been plenty of talk surrounding India’s Republic Day. More than 80,000 Indian police and paramilitary officers will be in the streets during the parade Monday, ABC News reported. Below are facts and photographs centered on one of the most important national holidays in India.

Indian Air Force fighter jets Indian Air Force Sukhoi Su-30MKI fighter jets fly overhead during a full dress rehearsal for the Republic Day parade in New Delhi. Photo: Reuters/Adnan Abidi

The Constitution of India signed by 284 Constituent Assembly members became effective Jan. 26, 1950. It is the longest constitution in the world, with 117,369 words in its English translation, BBC News reported. Before its adoption, India was ruled under the British Empire’s Government of India Act 1935. Jan. 26 was chosen as the designated date of Republic Day because it coincides with the anniversary of the Purna Swaraj, or Declaration of the Independence of India.

Indian Air Force soldiers Indian Air Force members rehearse for the Republic Day parade on a cold and foggy winter morning in New Delhi. Photo: Reuters/Ahmad Masood

Republic Day is one of three national holidays in India. Celebrations last for three days, with ceremonies held throughout the country. However, the main celebration and parade takes place in the national capital New Delhi at the Rajpath before the president of India, the Times of India said.

Indian Army weapon systems Indian Army’s BrahMos weapon systems are displayed during a full dress rehearsal for the Republic Day parade in New Delhi. Photo: Reuters/Adnan Abidi

While India’s prime minister takes center stage on India’s Independence Day, its president has the spotlight on Republic Day. Each year, a different foreign head of state is invited by the Indian government to the Republic Day parade as an official guest. Last year, Japanese Prime Minister Shinzo Abe was the chief guest, as the Washington Post reported. This year, Obama will join India’s President Pranab Mukherjee and Prime Minister Narendra Modi at the parade Monday. He is the first sitting U.S. president to attend India’s Republic Day observance.

Indian soldiers Military personnel march during the full dress rehearsal for the Republic Day parade in New Delhi. Photo: Reuters/Adnan Abidi

A large number of representatives of the Indian army, navy and air force take part in the Republic Day parade in New Delhi. Dozens of aircrafts fly over Rajpath during the parade. A 21-gun salute is given to the president and national flag of India during the flag-hoisting ceremony, according to NDTV

Indian soldiers Military personnel march during a full dress rehearsal for the Republic Day parade in New Delhi. Photo: Reuters/Adnan Abidi

A slew of major national awards -- including the Veer Chakra, Maha Veer Chakra, Param Veer Chakra, Kirti Chakra and Ashoka Chakra -- are awarded to deserving candidates on Republic Day, the Times of India said.

India's national flag A soldier marches as India’s national flag flutters during a rehearsal for the so-called Beating Retreat ceremony in New Delhi. Photo: Reuters/Adnan Abidi

India’s national flag was designed by freedom fighter Pingali Venkaiah, and it was adopted in 1947, a few days before India’s independence from the U.K. government, according to the Hindu. Even after India’s independence, people were allowed to hoist national flags over their homes only on national days. The Flag Code of India changed this rule Jan. 26, 2002, allowing flags to fly on any day, according to the Bureau of Indian Standards.

India's Republic Day parade Artists wait for their turn to perform during a media preview for the Republic Day parade in New Delhi. Photo: Reuters/Anindito Mukherjee

Rajendra Prasad was the first elected president of independent India and the only president to serve two terms in office. Prasad was a freedom fighter during the Indian independence movement, according to the Hindu.

India's Defense Ministry A general view shows the Indian defense ministry, left, and home ministry buildings, which are lit up ahead of the Republic Day celebrations in New Delhi. Photo: Reuters/Anindito Mukherjee

Important government buildings in India are decorated with lights as part of Republic Day celebrations, the Times of India said.

India's Republic Day parade Band members of security forces rehearse for the Republic Day parade on a foggy winter morning in New Delhi. Photo: Reuters/Adnan Abidi

Republic Day celebrations begin Jan. 26 and end with the annual Beating Retreat ceremony Jan. 29, when a band plays the famous Christian hymn “Abide With Me.” Authored by Scottish Anglican Henry Francis Lyte, the tune is believed to have been a favorite of Mahatma Gandhi, the parent of India’s independence movement, the Times of India said.