I grew up in a Maharashtrian Indian household. Every year in September or October my mom fasted for 9 days straight. It is a hard fasting period for her. She'd just have fruits and milk. These 9 days in September or October mark the Navratri festival which is a Hindu celebrated every year in the autumn. The last day of Navratri is Dusshera or Vijayadashami another major festival. Navratri rejoices Goddess Durga in her nine forms and Dussera celebrates the victory of Lord Ram over Ravan. But India is full of surprises. West Bengal in India further brings to you the famous Durga Pujo and the belief behind this celebration records the victory of Goddess Durga over the demon Mahishasur.
Festivities for Navratri and Durga Pujo commenced on 29th September and will go on till Dussera which is on the 8th October.
Navratri, Durga Pujo and Dussera are not exactly connected but the coincidental occurrence of all leads to a bigger and sparked celebration. In metropolitan Indian cities, you may be able to witness all three festival celebrations, Dussera of course on the last day of the festivities. Navratri and Durga Pujo, both, idolise Goddess Durga. Gujarat, Rajasthan and Maharashtra of West India celebrate Navratri while West Bengal in East India celebrates Durga Pujo. Other states of India cherish these festivals too. In Mysore, Karnataka a 10-day long Dussera festival is held every year.
Navratri and Durga Pujo also differ with regards to the food that is consumed during this time. During Navratri, devotees observe fasting for 9 days and refrain from consuming onion, garlic, eggs, meat and alcohol. During Durga Pujo, however, this is a time when Bengalis indulge in non-vegetarian specialities.
Durga Pujo at Kolkata, West Bengal
If you think you're a pub hopper, we bet during Durga Pujo you'll turn into a pandal hopper. Every pandal is extravagant and tells a story. The preparations for this festival is as grand as the festival itself. Hop pandals, indulge in Bhog (blessed food that doubles up as a complete meal as opposed to prasad) and do the Dhunchi dance.
Navratri in Gujarat
Dazzling dresses, midnight food and dandiya dance is the long story short for how Navratri is celebrated in Gujarat. In Gujarat, Navratri is celebrated with the Garba (garbha - a symbol of woman's fertility) and Dandiya-Raas (Dandiyas are decorated bamboo sticks) dance. The dance starts around 8-9 pm and goes on till 4 am sometimes.
Dusshera in Mysore
The Mysuru Dusshera festival is grand as it gets. It starts on the first day of Navratri/Durga Pujo and ends with a massive Dusshera celebration. On the day of Dusshera, a traditional possession known as Jumboo Savari is held on the streets of Mysore. The ceremonies and a major procession are traditionally managed by the king of Mysuru. The festival committee comes up with a list of programmes and special events every year filled with activities, cultural shows, exhibitions and food melas(fairs).
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Fun fact. This 10 day period is also a big deal for most Goddess temples in India. Temples have extraordinary and long aartis (part of puja) around this time. In this period, you can also see the Ramlila, a play which is the dramatic folk re-enactment of the life of Rama. There are also various dance workshops to learn the Garba and Dandiya. They begin couple of weeks before Navratri and go on till the seventh or eight day of Navratri.
It's great if you can visit the respective states. But, if you can't, most major cities in India celebrate these festivals and would have something going on. Households across India have belief systems that differ from each other and hence the approach they take for practising the small-big things vary during these festivals. At my home, on the last day of Navratri, my mom used to invite 9 young girls, wash their feet and offer food to them. As a kid, other than my home, I was also invited to a lot of houses in my neighbourhood.