In India, the festival starts on the new moon day falling between September 15 & October 15. In East Asia, it starts on the 9th day of the 9th lunar month [around the same time period].
In India, the primary theme is the celebration of truth over evil. It is celebrated as Garbha-Dandiya, Ramlila, Golu and Durga Pooja in various parts of the country (explained in detail below). It is probably the most important Indian festival you have never heard of. Essentially, it is an art festival and the celebration of good over the evil.
Women take a central stage in this festival and it is a celebration of femine qualities such as dance, music and decoration. It is celebrated over 10 days in September-October. It is also a reminder of historic status of women in India and how they held lot more power in ancient India.