Gudi Padwa is a Marathi/Hindu festival that marks the beginning of the new year according to the lunisolar calendar, primarily celebrated in Maharashtra. The other three (Bhogali Bihu, Pongal, Onam) are all harvest festivals celebrated in different regions of India (Assam, Tamil Nadu, Kerala). Gudi Padwa is the odd one out because it is a New Year celebration, not a harvest festival.