The event was declared by the 1969 Universal Postal Congress in Tokyo as a means to mark the anniversary of the Universal Postal Union's (UPU) creation in 1874.
The purpose of World Post Day is to bring awareness to the Post's role in the everyday lives of people and businesses, as well as its contribution to global social and economic development.
As a result, the UPU's member countries are encouraged to organize their own national activities to celebrate the event, including everything from the introduction or promotion of new postal products and services, to the organization of open days at post offices, mail centres and postal museums.
For countries participating in the UPU International Letter-Writing Competition, national winners are often honoured on 9 October.
Source: Universal Postal Union (UPU)