Why is the festival of Makar Sankranti celebrated, what is its religious and mythological significance and when is the festival of Sankranti?

Dakshinayan is the night of the gods, Uttarayan is the day
According to the scriptures, when the Sun stays in Dakshinayana, that period is called the night of the gods and the six months of Uttarayan are called days. Dakshinayana is considered a symbol of negativity and darkness and Uttarayan is considered a symbol of positivity and light. It is believed that on the day of Makar Sankranti, the deities descend to earth to receive the gods, to obtain the material offered in the yagya, and through this path the virtuous souls leave their bodies and enter heaven etc. does. Surya himself goes to meet his son Shani at his house.
According to Sanatan beliefs, on the day of Makar Sankranti, Lord Surya himself visits his son Shani at his house. Since Shani Dev is the lord of Capricorn, the effect of Shani gets weakened only when the Sun enters his house. Because any kind of negative energy cannot stand in front of sunlight. It is believed that by worshiping Sun on Makar Sankranti and donating related to it, all the defects of Shani are removed.

What are the mythological beliefs associated with Makar Sankranti?

According to the scriptures, on the day of Makar Sankranti, Goddess Gangaji, who emerged from the thumb of Lord Vishnu, followed Bhagirath. After going to the ashram of Kapil Muni, they joined the ocean and the son of Maharaj Sagara, the ancestor of Bhagirath, became free. That is why on this day a huge fair is organized in the ashram of Kapil Muni in Gangasagar of Bengal.

Bathing meditation of Gangasagar has great importance in Bengal:

Bathing in Gangasagar has special significance on the day of Makar Sankranti. According to another story, after the end of the Mahabharata war, Bhishma Pitamah kept waiting for the sun to be Uttarayan. He gave up his life on Makar Sankranti. It is also believed that on this day Mother Yashoda fasted to get Lord Krishna.
Importance of bathing and donating in the Ganges river on the day of Makar Sankranti.

According to Padma Purana, charity is of great importance on the day of Uttarayan of the Sun i.e. on Makar Sankranti. Taking a bath before sunrise on the day of Makar Sankranti is also of great importance. By doing this the fruit of ten thousand cows is obtained. On this day, donating woolen clothes, blankets, dishes made of sesame and jaggery and khichdi brings blessings of Lord Surya and Shani Dev. If seen, after bathing in a pilgrimage, river and sea in the Uttarayan month of the sun, one gets freedom from all kinds of troubles.
The festival of Makar Sankranti is different in different states. Known and celebrated by different names...
Makar Sankranti is called Khichdi festival in Uttar Pradesh. On the day of Makar Sankranti, Sun God is worshipped and Arghya is also offered. Khichdi made from rice lentils is also eaten and donated. Donating sesame seeds and gunas also gives freedom from sorrows. There is also a practice of donating sesame seeds and gunas.
In Gujarat and Rajasthan, Makar Sankranti is celebrated as Uttarayan festival. On this day kite festival is organized in both the states with great pomp.
In Andhra Pradesh, the three-day festival is celebrated by the name of Sankranti. Whereas in Tamil Nadu Sankranti is celebrated as Pongal as the main festival of farming. On this day, dalanchawal khichdi is cooked in ghee and fed.
In Maharashtra also it is celebrated as Makar Sankranti or Sankranti. Here people eat and donate gajak and sesame laddus. Greet each other with gifts.
In West Bengal, on the day of Makar Sankranti, Ganga Sagar Fair is organized on the Hooghly River. Hence in Assam it is celebrated as Bhogali Bihu.