September 17
Overview
Holidays & Observances
Australian Citizenship Day
Australian Citizenship Day honors new citizens and celebrates the values of democracy, respect, and freedom that unite the nation.
Christian feast day:
Albert of Vercelli, Ariadne of Phrygia, BlessedCecilia Eusepi, Stanislaus Papczyński, Hildegard of Bingen, Lambert, Robert Bellarmine, Satyrus of Milan, Socrates and Stephen, Zygmunt Szczęsny Feliński, September 17 (Eastern Orthodox liturgics)
A day marking the feast of numerous saints in Catholic and Orthodox traditions.
Constitution Day and Citizenship Day, observed on the previous Friday if it falls on a Saturday, the following Monday if on a Sunday; and the beginning of theConstitution Week(United States)
An annual observance commemorating the signing of the U.S. Constitution and celebrating American citizenship.
Heroes' Day (Angola)
A national holiday in Angola honoring those who fought for the nation’s independence.
Marathwada Liberation Day(Maharashtra)
A regional observance marking the liberation of Marathwada from Nizam rule.
National Unity Day (Belarus)(since 2021)
A Belarusian public holiday celebrating the country's reunification in 1939.
Operation Market Garden Anniversaryis still remembered with parachuting and dedications on this day. (Netherlands)
The anniversary of the largest airborne operation of World War II, remembered with ceremonies and commemorations in the Netherlands.
Teachers' Day(Honduras)
A day recognizing and honoring the contributions of teachers to Honduran education and society.
Albert of Vercelli
Commemoration of Saint Albert of Vercelli, a 13th-century Dominican friar and bishop.
Events
Highest Galician nobility led by Pedro Fróilaz de Traba and the bishop Diego Gelmírez crown Alfonso VII as "King of Galicia".
In 1111, Galician nobles led by Pedro Fróilaz de Traba and Bishop Diego Gelmírez crown Alfonso VII as King of Galicia, marking a key moment in the consolidation of his rule.
The Battle of Myriokephalon is the last attempt by the Byzantine Empire to recover central Anatolia from the Seljuk Turks.
In 1176, the Byzantine Empire's final campaign to reclaim central Anatolia ends in defeat at the Battle of Myriokephalon against the Seljuk Turks.
Louis the Great's daughter, Mary, is crowned "king" of Hungary.
In 1382, Mary, daughter of Louis the Great, is crowned king of Hungary, becoming one of the few female rulers to hold the title.
Thirteen Years' War: A Polish army under Piotr Dunin decisively defeats the Teutonic Order at the Battle of Świecino.
During the Thirteen Years' War in 1462, Piotr Dunin leads Polish forces to a decisive victory over the Teutonic Knights at Świecino.
The first Finnish-language book, the Abckiria by Mikael Agricola, is published in Stockholm.
In 1543, Mikael Agricola's Abckiria becomes the first book printed in Finnish, laying the foundation for the Finnish written language.
The Treaty of Bergerac is signed between King Henry III of France and the Huguenots.
The 1577 Treaty of Bergerac concludes a round of the French Wars of Religion, granting limited freedoms to the Huguenots under royal authority.
Polish–Ottoman War: The Ottoman Empire defeats the Polish–Lithuanian Commonwealth during the Battle of Cecora.
In 1620, Ottoman forces defeat the Polish–Lithuanian Commonwealth at the Battle of Cecora, marking a turning point in the Polish–Ottoman War.
Sweden wins a major victory at the Battle of Breitenfeld against the Holy Roman Empire during the Thirty Years' War.
At the Battle of Breitenfeld in 1631, Swedish King Gustavus Adolphus secures a pivotal victory over the Holy Roman Empire during the Thirty Years' War.
The Battle of Vilanova is fought between Portugal and Spain during the Portuguese Restoration War.
In 1658, Portuguese troops engage Spanish forces at the Battle of Vilanova, pressing their fight for restored independence.
Births
Charles the Simple
Charles the Simple was the King of West Francia from 898 to 922 and ruler of Lotharingia. He is remembered for granting Viking leader Rollo lands that became Normandy.
James of Portugal
James of Portugal was a Portuguese prince who became a cardinal of the Catholic Church at a young age. He combined royal lineage with high ecclesiastical office.
Celio Calcagnini
Celio Calcagnini was an Italian Renaissance astronomer, humanist, and mathematician. He made contributions to early astronomical observations and scientific correspondence.
Paul V
Pope Paul V, born Camillo Borghese, led the Catholic Church from 1605 until his death in 1621. He was a patron of the arts and oversaw significant church-building projects.
Edward Fortunatus
Edward Fortunatus was a German margrave known for his tumultuous rule over the Baden territories and lavish lifestyle. His reign was marked by dynastic conflicts and financial troubles.
John Prideaux
John Prideaux was an English bishop and academic leader who served as Vice-Chancellor of Oxford University and Bishop of Worcester. He made significant contributions to university governance and theological scholarship.
Francesco Sacrati
Francesco Sacrati was an Italian Baroque composer known for pioneering opera. His works influenced the development of early seventeenth-century musical drama.
Ranuccio II Farnese
Ranuccio II Farnese was Duke of Parma and Piacenza from 1646 to 1694, notable for his patronage of the arts and courtly reforms.
Hans Herr
Hans Herr was a Swiss Mennonite bishop who led his community’s migration to North America. He is remembered as a pioneering spiritual leader among the Amish.
Deaths
Remistus
Remistus was a prominent 5th-century Roman general serving under Emperor Avitus.
Unni
Unni was the Archbishop of Hamburg-Bremen, known for his missionary work in Northern Europe.
Li Jingsui
Li Jingsui was a prince of the Southern Tang kingdom during the Five Dynasties and Ten Kingdoms period in China.
Hugh Magnus
Hugh Magnus was co-king of France alongside his father, King Robert II, until his death in 1025.
Conan III
Conan III was the Duke of Brittany from 1112 to 1148, known for his strong rule and dynastic alliances.
Hildegard of Bingen
Hildegard of Bingen was a German abbess, composer, and polymath celebrated for her visionary writings and music.
Robert III
Robert III, known as Robert of Béthune, was the Count of Flanders from 1305 to 1322, noted for his leadership and diplomacy.
Michael de la Pole
Michael de la Pole was the 2nd Earl of Suffolk, an English nobleman and soldier who died at the Battle of Agincourt.
Constantine II
Constantine II was the last native Tsar of Bulgaria, whose reign ended with the Ottoman conquest in the early 15th century.