India, Sept. 28 -- Every major consumption market has its big moment. In the United States, retailers calibrate their year around the November-December holiday stretch, when Black Friday and Christmas together generate almost 19-20% of annual retail sales. In China, Singles' Day (11.11) has become a global spectacle, with platforms like Alibaba and JD.com driving more than RMB 1.44 Tn ($200 Bn) in gross merchandise value (GMV) during a single week.

India's equivalent is Diwali, the centrepiece of the festive quarter that stretches from September through December. It is the country's single largest consumption window, and its significance is only growing.

For brands and retailers, this is the moment of truth. Inventories are stocked mont...