This is true in India Baskin & Robbins. On every 31st (7 days a year), Baskin & Robbins in India offers 31% discounts. I got to know this from my friend. Its a pretty useful info to know for ice-cream lovers.

If you look closely at Baskin & Robbins logo, there's a 3 in B and 1 in R which signifies the 31 flavors of ice-creams they have and the 31% discount on every 31st is also for the same reason.