पश्चिम रेलवे की शान, पश्चिम सुपरफास्ट एक्सप्रेस मेरी जान - Abdul Rehman

Basically all of these festivals are Harvest festivals. Pls refer /blog/post/2123260
India has been an agriculture focused nation for ages and during mid January, most of the regions prepare themselves to harvest the ripe crops standing in their fields. Pongal, Sankranti, Bihu, Lohri, Uttarayan etc. are observed to celebrate a good crop and to thank gods for the same.
The second theory for celebrating this relates to Astronomy. "Sankranti actually means transmigration of the Sun from one Rāshi to the next. Since there are 12 Rashi's, there are 12 sankranti's in the...
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year. Out of these, the one that falls on 14th or 15th January is Makar (Aquarius) Sankranti as the Sun enters Makar Rashi. This sankranti is considered more important than other sankranti's because after this date, the Sun is considered becoming 'Uttargami' . In other words, from this particular day, earth starts shifting its rotation axis towards Northern direction. This results in reduction of winter, increase in average temperature and days becoming longer than night.
(I know it has been too much gyan.. :) )