India 'celebrates' four of them: Republic Day, Independence Day, Gandhi Jayanti, and Children's Day. The others, like Teacher's Day and Mother's Day, are more on the scale of observances.
What separates national festivals from the others is the number of levels they happen at.
For one, the government does not merely declare holidays but becomes one of the participants. On Republic Day and Independence Day, there are formal events - including a march-past and flag-hoisting - in all the state capitals, district headquarters, corporations and municipalities, panchayats… and so it goes. Step outside the government, and you have offices, educational institutions, co-operatives and other organisations doing their bit on corresponding scales.
If you want to witness official celebrations, the place to be in is New Delhi. The spectacular pageants, grand march-pasts, floats, cultural tableaux and shows have tens of thousands of people lining the roads to view them.
The essence of the mood, however, comes from the participation of the community as an entity, however platitudinous that might sound.
In fact, Republic Day and Independence Day have slowly gained almost the same air that other festivals have. You have people sending greeting cards, wishing each other, organising entertainment, eating out, and generally letting their hair down.
Gandhi Jayanti and Children's Day are more muted. Gandhi Jayanti is officially significant but does not evoke the same response from the people as Independence Day and Republic Day.
Children's Day is more or less confined to schools. So is Teacher's Day, when many schools follow the practice of observing a role reversal: getting the students of the higher grades to take classes for the lower grades while the teachers themselves sit among the students.
The birthdays of other national leaders are not much more than official observances. The states of India celebrate their own days. The bigger cities, especially the state capitals, hold programmes and events that specifically display the highlights of the state's culture and way of life.