Why are Curries dated?

[Mr. Ected]

According to Herbie at Herbie's Spices:

First of all, a lot depends on the freshness of the curry powder when it is purchased. We recommend only buying spices that have a Best Before date on them.

Secondly, the method of storage will affect the shelf life of a curry powder. Ground spices should be stored in airtight packaging and kept away from extremes of heat, light and humidity.

Thirdly, when correctly stored, curry powder should retain its optimum flavour for a period of around 18 months.