The celebration of Diwali and Dusshera in India often marks the celebration of the victory of Rama. With Lord Rama, Devi Sita is also worshipped with great pomp and splendor. Apart from that, on Ram Navami signifying the birthday of Lord Rama and Vivah Panchami that enacts the wedding of Ram and Sita are also celebrated. While the former is celebrated around March-April, the later takes place on the fifth day of full moon in November to December.
Places Of Worship
Sita is worshipped more or less all over India, and even in Nepal. In fact, she is greatly associated with Hinduism. There is no particular area, where she is worshipped, but in places of North India like Mithila, she has immense significance. There is no particular time when she is worshipped, but several people find out specific time to worship her.