What is the cultural importance of Chhath Mahaparv

The rituals and celebrations of Chhath are celebrated across 4 days - The Nahay khay, the Kharna, the Sandhya Arghya, and the Usha Arghya.
This year, it began on November 5 with ‘Nahay Khay’ which means ‘bath and eat’. All devotees take a dip in a river or pond to purify their body and soul, and then have a simple meal with rice, dal, and ‘kaddu bhat’. Then on the next day comes Kharna, where devotees observe a fast all day, and eat food after sunset. The evening meal, known as ‘Kharna’, is prepared with earthen pots, and marks the time after which the devotees observe a Nirjala fast for 36 hours. On day 3, devotees give Sandhya Arghya to the setting sun. They stand knee-deep in water, facing the sun, and offer their prayers. And then on the last day, the same thing is done with the rising sun.