India is a rich land which has attracted invaders from Central Europe and Asia who left their imprint on this land, its religions and its lifestyles over 40 centuries. As a result, today, Indian celebrates more festivals than any other country. Nonetheless, Indians are known to celebrate all the festivals with great fan fare and importance.
Festivals in India are determined by the Solar & Lunar positions & they may fall in a different month as specified here.

January
Makar Sankranti, Lohri, Pongal, Thai Pusam, Float Festival, National Kite Festival, Bikaner Festival, Pattadakal Dance Festival, Id-ul-Fitr, Vasant Panchami

February
Mahashivratri, Goa Carnival, Desert Festival, Nagaur Fair, International Yoga Week, Elephant Festival, Deccan Festival, Taj Mahotsav, Surajkund Crafts Mela, Chapchar Kut, Islands Tourism Festival

March
Holi, Gangaur, Jamshed-e-Navroz, Ramnavami, id-ul-Zuha, Mahavir Jayanti, Khajuraho Dance Festival, Elephant Festival, Hoysala Mahotsava, Ellora Festival

April
Good Friday, Easter, Baisakhi, Gudi Padva or Ugadi, Pooram, Maharram, Buddha Purnima, Mewar

June
Ganga Dussehra, Hemis Festival
July
Rathyatra, Guru Purnima

August
Janmashtami, Onam, Nag Panchami, Rakshabandhan, Ganesh Chaturthi

September
Tarnetar Mela

October
Navratri, Durga Puja, Dussehra, Marwar Festival

November
Sharad Purnima, Diwali, Guu Purab, Ka Pomblang Nongrem, Sonepur Fair, Pushkar Fair, Hampi Festival

December
Christmas, Konark Dance Festival