World Postcard Day on 1 October 

Every year on the 1st of October, postcard lovers around the world celebrate World Postcard Day. It's a relatively new occasion but it has a very old heart. The date was chosen because the first official postcard was issued by the Austrian Post on October 1st, 1869. The first postcard was a light-brown rectangle called the Correspondenz-Karte featuring a pre-stamped postage and space for a short message, and it was designed by an Austrian postal clerk named Emanuel Herrmann. 

World Postcard Day itself grew out of Postcrossing's celebration of the 150th anniversary of the postcard in 2019, when a worldwide campaign of exhibitions, meetups, special cancellation marks, and workshops was organised to mark the occasion. The following year it became an annual celebration, and it has been observed ever since on the 1st of October.