This public holiday is always celebrated on June 23. June 23 is Luxembourg's National Day (Celebration publique de l'anniversaire du souverain) and the official birthday of the Grand Duke although no Grand Duke/Duchess has ever had a real birthday that fell on this day.
The Duke's birthday doesn't even commemorate the birth of a Duke, but a Duchess - the Grand Duchess Charlotte who ruled Luxembourg from 1919 - 1964. Charlotte was actually born on January 23, 1896, but the celebrations were shifted to June so that the celebrations should have more favourable weather.
The day was made a national holiday in 1941, and the date of June 23 was fixed by Ducal decree in 1961. So , despite the current Duke being the grandson of Charlotte, the June 23 date has remained the National Day.
On the eve of National Day, a torchlight procession lights the streets beginning at 10 in the evening. A spectacular fireworks display is held in the Petrusse Valley and a mass is celebrated at the cathedral. After the fireworks, the city of Luxembourg City turns out for a massive party with waffles, sausages, beer, music, and dancing in the streets. Official ceremonies, military parades, and a 101-cannon salute are held on National Day itself.
Luxembourg's economy is largely based on its highly developed financial sector. The country is the world's second largest investment fund center (next to the United States) and the most important private banking center in the Eurozone. As of 2011, Luxembourg had the second highest Gross Domestic Product per capita in the world and the fourth highest Quality of Life index.