Diwali traditionally falls on Amavasya Tithi of Kartik month, which begins at 3:45 PM on October 20 and ends at 5:55 PM on October 21. According to multiple Panchangs, Diwali should be celebrated on October 21 as on that day Amavasya will be at both sunrise and sunset. Laxmi puja should be done between 5:46 PM and around 8:10 PM.