Mahalaya is a significant day in the Hindu calendar, particularly celebrated in West Bengal, India, and Bangladesh. It marks the beginning of the festival of Durga Puja, which celebrates the victory of good over evil. Mahalaya is derived from Sanskrit words meaning "Great Abode" and signifies the goddess Durga's journey from Kailash to Earth. The day is celebrated with the recitation of the hymn "Mahishasura Mardini" and various customs and traditions.