Diwali 2025: Should you celebrate on October 20 or 21?

Dubai: Every year, as autumn settles over, a familiar question emerges: When exactly is Diwali? In 2025, this question has sparked particular confusion, with some celebrating on October 20 and others on October 21. The answer reveals the complexity of India's lunar calendar system.

A tithi, which means date in the lunar calendar, represents the time it takes for the Moon to move 12 degree relative to the Sun. Unlike the standard 24-hour solar days, tithis don't line up neatly. A tithi can start and end at any time of day, even spanning two calendar days.

Since the new moon period stretches across two dates on the Gregorian calendar, it creates natural confusion about which day to celebrate.

The key to resolving this lies in understanding 'pradosh kaal', the twilight period after sunset considered most auspicious for evening prayers. The Pradosh Kaal falls on the evening of October 20 between 5:58 pm and 8:25 pm, with another auspicious period called Vrishabha Kaal overlapping from 7:08 pm to 9:03 pm.

This timing makes October 20 the ideal day for celebrations. Due to the absence of Amavasya on the night of October 21, some rituals traditionally associated with the new moon cannot be performed the next day. However, both Pradosh Kaal and Amavasya night coincide on October 20, making it the ideal day for celebrating Diwali.

Geography plays a surprising role. Astrologers advise that in cities where sunset happens on or before 5:30 pm, Diwali should be observed on October 21, whereas in places where sunset is after 5:30 pm, the celebration can take place on October 20. This explains why most of India celebrates on the 20th, but some eastern regions observe it on the 21st.

The celebrations span five days: Dhanteras on October 18, Choti Diwali on October 19, main Diwali on October 20, Govardhan Puja on October 22, and Bhai Dooj on October 23. Each day carries its own significance and rituals.

The confusion stems from the Amavasya Tithi, the lunar phase that determines Diwali's date, falling across two consecutive days. But this isn't a flaw, it's a feature of a sophisticated calendar system that has tracked celestial movements for thousands of years, long before modern astronomy.