Why is Chhath Puja celebrated in March-April too?

Chhath Puja is celebrated twice a year, during the months of Chaitra (March-April) and Kartik (October-November) in the Hindu calendar. Chaiti Chhath is believed to mark the descent of the Yamuna to Earth and coincides with the birth anniversary of Goddess Yamuna, HT reported. Notably, both festivals are celebrated by offering prayers to the Sun God in the same way.