As the only festival that has been carried on from the Vedic period, Chhath puja is indelibly associated with nature-worship for the well-being of humanity.
As the Sun God manifests his greatest power in the rising and setting sun, these two significant moments coincide with the two 'aragyas' or offering of river water to Lord Surya during the festival.
The morning glory of the rising sun and the majesty of the setting sun evoke a sense of power and awe among millions of devotees who come to pay obeisance to Lord Surya.