The holiday is in memory of 15 September 1947, when the Paris Peace Treaty with Italy came into force; under the Treaty, Italy ceded to the then Yugoslavia sovereignty over Upper Posočje, the Vipava Valley, the greater part of the Karst and a small part of Istria. A state ceremony was held on Wednesday in Portorož.

The President of the National Assembly, Urška Klakočar Zupančič, gave the keynote speech at the ceremony. Among other things, she said that the holiday is dedicated to the heroines and heroes of Primorska, the valiant fighters against subjugation, against denationalisation, against ideologies that create racial, national and ethnic inequalities, and against the dictatorship of single-mindedness. “Without them, we would not have our own country today,” she stressed.

One of the focuses of the ceremony was the life and work of Boris Pahor, a writer from Trieste who died this year.

The Return of Primorska to the Motherland Day has been celebrated since 2005, but it is not a work-free day.

75 years ago, Slovenia did not yet encompass all of today's territory. On the coastal strip between Trieste and Novigrad in Croatia, the Paris Peace Treaty foresaw the creation of an independent state, the Free Territory of Trieste. It was dissolved by the London Agreement in 1954, when Slovenia gained access to the sea. Historians estimate that approximately 140,000 Slovenians were left outside their motherland.