You're likely to see military parades and sombre tributes to fallen soldiers on Tuesday as Italy officially honours its armed forces.
The date comes with a traditional display of Italy's military power, with events held in cities all over the country.
November 4th doesn't come with a day off work as this is one of several 'non-holiday' holidays on the national calendar.
So what is it all about?
National Unity Day, or to give it its full title, Giornata dell'Unità Nazionale e delle Forze Armate ('Day of National Unity and the Armed Forces'), commemorates the end of World War I for Italy.
It's celebrated on November 4th, the day an armistice ended the fighting between Italian forces and the battered Austro-Hungarian Army in 1918.
The so-called Armistice of Villa Giusti, named after the estate in Veneto where it was signed the day before, ended hostilities in northeastern Italy and paved the way for Italian soldiers to occupy border regions in the Dolomites and on the Adriatic (modern-day Alto Adige/South Tyrol and Friuli-Venezia Giulia) that had previously belonged to Austria-Hungary's empire.
Map of Europe in 1923. Image: Fluteflute - CC BY-SA 2.5, Wikimedia CommonsItaly declared the anniversary a holiday in 1919, dedicating it to its troops and the new territories for which they had fought.
The incorporation of these areas, home to many ethnic Italians and Italian speakers, was seen by nationalists as completing the unification of Italy – hence the celebration of 'national unity'.
The occasion has been celebrated for 105 years since, making it one of Italy's oldest national holidays and one of the few to be observed before, during and after the Fascist era.
While protesters of the 1960s and 70s objected to what they saw as the glorification of militarism and nationalism, the holiday survived, though celebrations became progressively smaller.
In 1977 National Unity Day – which comes hot on the heels of the All Saints' Day holiday on November 1st – went from a public holiday to being marked on the first Sunday of November, thus abolishing the day off.
How does Italy celebrate November 4th now?
These days celebrations take place on November 4th itself. The main event is a military display at the Altare della Patria in Rome's Piazza Venezia, attended by the Italian president and minister of defence.
The head of state lays a wreath over the Tomb of the Unknown Soldier or Milite Ignoto, who was buried at the monument on November 4th, 1921.
There is also a fly-past by the air force's Frecce Tricolori aerial display team – though this year's display was cancelled to avoid distracting workers securing a medieval tower that partially collapsed in Rome on Monday – and a changing of the guards outside the president's palace.
Ceremonies are held at war memorials and cemeteries around Italy.
Military sites are sometimes opened exceptionally to the public, while members of the armed forces perform exercises or concerts in town squares.
Does Italy have any other non-holiday holidays?
Yes. National Unity and Armed Forces Day is one of seven in Italy that are considered official but not public holidays. They include the day of Italy's patron saints Francesco and Caterina on October 4th, as well as the anniversary of the unification of Italy on March 17th.
That's in addition to nearly 30 national and international days of commemoration or celebration that Italy recognizes, including Holocaust Remembrance Day (January 27th), Europe Day (May 9th) and Christopher Columbus Day (October 12th).
Unlike Italy's 12 national public holidays, none of the above will get you the day off.
So when is the next public holiday in Italy?
Your next day off work in Italy is December 8th, the day when Roman Catholics mark the Immaculate Conception of the Virgin Mary.
After that, it's just a few weeks until Christmas Day, Saint Stephen's Day on December 26th, and New Year's Day.
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