Makar Sankranti

Ask why Diwali and Holi wander across the Gregorian calendar and Makar Sankranti does not, and the answer is that they are on different clocks.

Most major Hindu festivals are set by luni-solar reckoning: a lunar day within a lunar month, with an extra month inserted periodically so the months do not drift away from the seasons. The insertion keeps the festival roughly in its season but lets it swing across four or five weeks of the Gregorian year.

Makar Sankranti is set by the sun alone. It is the moment the sun crosses into the sign of Makara. Solar events do not wander, and so it lands on January 14 or 15 essentially every year.

The slow drift

But it does move, just very slowly, and the reason is the most interesting thing about it. Indian astronomy measures the sun's position against the fixed stars, the sidereal zodiac, rather than against the equinox. The equinox itself moves, precessing westward against the stars at about fifty arcseconds a year. Over a human lifetime that is unnoticeable. Over centuries it accumulates: the gap between the two systems, the ayanamsa, now stands at roughly twenty-four degrees.

So the sidereal entry into Capricorn slides forward through the tropical year by about one day every seventy to eighty years. Five hundred years ago the festival fell in the first week of January. Five hundred years from now it will fall around January 21.

What that does to the meaning

The day is described as the beginning of uttarayana, the sun's northward turn, which is the winter solstice, around December 21. The two coincided long ago. They no longer do; the drift has opened a gap of over three weeks, and it is widening. The festival is now kept on a date that no longer is the event it is said to mark.

Whether to correct this is a real and unresolved dispute. India's calendar reform committee under Meghnad Saha in the 1950s recommended a tropical basis, which would have pulled the date back toward the solstice. Traditional almanac makers did not adopt it, and the sidereal reckoning remains in use. The gap continues to grow.

The sun's entry into Makara is a single astronomical instant observed across India, and what happens on it looks entirely different depending on where you are.

• Punjab keeps Lohri on the evening before, around a bonfire, with sesame, jaggery, popcorn and peanuts thrown into it, and songs about Dulla Bhatti. The following day is Maghi, which for Sikhs carries the memory of the forty at Muktsar.
• Assam keeps Magh Bihu, or Bhogali Bihu, the festival of feasting: temporary huts of bamboo and thatch built and burnt, buffalo fights in some districts, and an enormous amount of food.
• Gujarat keeps Uttarayan by flying kites from every roof in Ahmedabad from dawn, with a second round of lantern kites after dark.
• Tamil Nadu keeps Thai Pongal, four days built around rice boiling over in a new pot.
• Bengal keeps Poush Sankranti with rice-flour pithe, and a large bathing fair at Gangasagar where the river meets the sea.
• Karnataka keeps Sankranthi with ellu bella, a mixture of sesame, jaggery, groundnut and coconut, exchanged with the line asking the recipient to take it and speak sweetly.
• Maharashtra exchanges tilgul laddus with the same sentiment, and married women hold haldi-kunku gatherings.
• Uttar Pradesh keeps Khichdi, and the Magh Mela at Prayagraj takes its largest bathe of the year on this morning.

Calling all of this one festival is defensible only at the level of the astronomy. The bonfire in Punjab and the kites in Gujarat are not variants of a common rite; they are separate observances that happen to be triggered by the same position of the sun.