What's the difference between Ram Navami and Maha Navami?

Ram Navami marks the birth of Lord Ram and falls on the ninth lunar day of Chaitra Navratri, usually in March-April. Maha Navami is devoted to Goddess Siddhidatri, the ninth form of Durga, and is observed on the ninth day of Sharad Navratri. Maha Navami marks the goddess's victory over Mahishasura and is followed by Dussehra on the tenth day.