January – March
Pongal (Jan, Tamil Nadu — harvest, kolam-decorated houses). Republic Day (Jan 26, Delhi — India Gate parade). Kumbh Mela (rotates every 3 years between Prayagraj, Haridwar, Ujjain, Nashik). Holi (mid-March, north India — colour throwing).
April – June
Baisakhi (mid-April, Punjab — Sikh New Year, biggest at Golden Temple). Rath Yatra (June-July, Odisha's Puri). Onam (mid-Aug, Kerala — flower carpets, boat races). Independence Day (Aug 15).
July – September
Ganesh Chaturthi (early Sep, Maharashtra — Ganpati processions). Onam (as above, if late). Durga Puja (Sep-Oct, Kolkata — 4 nights of processions).
October – December
Dussehra (early Oct, north-wide — Ravana effigies burnt). Diwali (mid-Nov — lights, sweets, family). Guru Nanak Jayanti (mid-Nov, Punjab). Pushkar Camel Fair (early Nov). Hornbill Festival (Dec, Nagaland — tribal culture). Christmas + New Year (Dec, Goa + Bengaluru + Mumbai — beach party season).