Festival of lights. Multiple stories - Rama's return to Ayodhya (North), Krishna slaying Narakasura (South), Lakshmi's appearance from Samudra-manthan, Vishnu's pushing Bali to patala. Diwali-eve = Lakshmi puja. The supreme business-new-year start.
Why this date - the science
Amavasya = new-moon = the darkest night. Lighting 1000s of diyas creates astronomical-scale illumination. Modern science: the COLLECTIVE psychological lift of light-in-darkness is measurable.
Ayurvedic wisdom
Karthika = peak autumn into early winter. Vata + pitta both moderating. Diwali sweets - kaju-katli, badam-burfi, soan-papdi, gulab-jamun - high in ghee + nuts. Exactly the calorie + healthy-fat density the body needs before winter. The traditional pre-Diwali abhyanga-snana (oil-bath at dawn on Narak-chaturdashi) is the supreme Ayurveda post-monsoon detox.
For the family & mind
The largest annual household-celebration. Cleaning of the home (Diwali-cleaning) - psychological renewal. New clothes, family gatherings, exchanging sweets with neighbours - strengthens ALL social-ties before winter. Marriages, business-openings, major purchases all auspicious on Dhanteras. The 5-day festival anchors the year.
Go deeper - every Hindu festival aligns spiritual, astronomical, ayurvedic and emotional layers on the same day. Read the full festival science explainer, check today's Panchang, or see the full festival calendar.