How the Kumbh dates are fixed: the sky behind the snan

Most festivals fall on a date in the calendar. The Kumbh is different: it is held when certain planets reach certain signs of the zodiac. That is why the gap between two Kumbhs at the same place is close to twelve years, but not always exactly twelve.

The planet that matters most is Jupiter, called Guru or Brihaspati. It takes a little under twelve years (about 11.9) to go once around the Sun, so it spends roughly a year in each of the twelve signs.

Each Kumbh site is linked with a position of Jupiter and the Sun. In the traditional rules, the Kumbh at Haridwar falls when Jupiter is in Aquarius (Kumbha), at Prayagraj when Jupiter is in Taurus and the Sun in Capricorn, and at Ujjain and Nashik when Jupiter is in Leo (Simha).

Because Nashik and Ujjain share Jupiter in Leo, both are called Simhastha. For Nashik, the most important snan days come when the Sun also enters Leo, in the monsoon months of Shravan and Bhadrapada.

Seen from Earth, Jupiter seems to move backwards for a few months every year. This is called vakri (retrograde) motion. Around a sign change, it can slip back into the previous sign and enter Leo again, so the Simhastha period at Nashik and Trimbakeshwar stretches well beyond a single year.

Since Jupiter's year is slightly shorter than twelve of ours, a Kumbh sometimes comes after eleven years instead of twelve. Haridwar, for example, held its Kumbh in 2021, eleven years after 2010.

Panchang makers work out the exact tithis and planetary positions. The akhadas and the government then announce the Amrit Snan days, routes and arrangements. Always follow those official announcements; Kumbh Path's calendar marks dates as announced or as expected.