It was on 12 October 1810 that Ludwig and Therese invited the townspeople of Munich to their wedding, sparking the tradition of Oktoberfest. Here's what the almanac says about it:
"The first Oktoberfest had its origins in Munich on this date in 1810. The occasion was a royal wedding: Ludwig, Crown Prince of Bavaria, was marrying Princess Therese of Saxony-Hildburghausen, and the royal couple wanted to invite all of Munich to their wedding reception. They threw a parade and a huge party in the field outside the city gates, culminating in a horse race. The citizens of Munich had such a good time that they decided to repeat the horse races at the same time the following year.
On the first anniversary of the royal wedding, the organizers added an agricultural show, to bring attention to the Bavarian farming industry. The horse races are no longer held, but the agricultural show remains a big part of Oktoberfest in Bavaria. Over the years, attractions have been added to the celebration: in 1818, organizers brought in a carousel and a couple of swings. They also set up a few modest beer stands. By the end of the century, the little stands had been replaced by huge beer tents and halls, sponsored by German breweries, and the carousel had grown into a full-fledged fair. In 1885, the beer tents were lit with electric lights for the first time.
The Oktoberfest was canceled on a few notable occasions during the 19th century — usually because of war or disease. In 1933, the swastika replaced the flag of Bavaria, and the festival was canceled for the duration of World War II. And in 1980, a bomb planted in a trash can by a right-wing extremist killed 13 people and wounded more than 200. And, unsurprisingly, it has been canceled in 2020 due to the coronavirus pandemic."
The official website, English version, is here:
https://www.oktoberfest.de/en?