It is tradition to hang ribbons from all available surfaces, including wearing one yourself. The Dragonborn don't remember when this celebration started, or why precisely – but it has become ingrained in their cultural memory.
It has evolved to include wearing ribbons from one year to the next, with some Dragonborn weaving their ribbons together in a braid so that others of their race can tell at a glance how many years they have seen. Some Dragonborn cities have produced specific crests on their ribbons, so that they can be used a display of where the Dragonborn has traveled. Some clutches do the same with family names and sigils.