325day.year
The First Council of Nicaea is formally opened, starting the first ecumenical council of the Christian Church.
The First Council of Nicaea convenes under Emperor Constantine, marking the first unified gathering of Christian bishops.
Called by Constantine the Great, the Council of Nicaea assembled over 300 bishops in what is now Iznik, Turkey. The council aimed to address the Arian controversy and establish doctrinal unity in the Christian Church. Delegates debated key theological points, culminating in the formulation of the original Nicene Creed. The council also set a unified date for Easter and addressed various church canons. Its outcomes shaped Christian orthodoxy and influenced ecclesiastical governance for centuries.
325
First Council of Nicaea
ecumenical council
491day.year
Empress Ariadne marries Anastasius I. The widowed Augusta is able to choose her successor for the Byzantine throne, after Zeno (late emperor) dies of dysentery.
Empress Ariadne of Byzantium marries Anastasius I, securing the imperial succession after Zeno’s death.
Following the death of Emperor Zeno, Empress Ariadne exercised her authority as Augusta to select her new consort. She chose Anastasius, a trusted palace official, who was proclaimed emperor upon their marriage. Anastasius enacted administrative reforms, improved fiscal management, and oversaw the construction of the Anastasian Wall defending Constantinople. His reign brought stability and strengthened the eastern Roman Empire. He ruled successfully until 518, leaving a lasting imprint on Byzantine governance.
491
Ariadne
Anastasius I
Augusta
Byzantine
Zeno
dysentery
794day.year
While visiting the royal Mercian court at Sutton Walls with a view to marrying princess Ælfthryth, King Æthelberht II of East Anglia is taken captive and beheaded.
King Æthelberht II of East Anglia is seized and executed at Sutton Walls, ending his dynasty’s ambitions.
While seeking to marry Mercian princess Ælfthryth in 794, King Æthelberht II attended the court at Sutton Walls. Instead of a royal match, he was arrested on suspicion of plotting against King Offa of Mercia. Æthelberht was beheaded, cutting short East Anglian hopes and consolidating Mercian dominance. His body was later venerated as a martyr, and his remains were reburied at Hereford Cathedral. The incident highlights the ruthless power struggles of Anglo-Saxon England.
794
Mercian
Sutton Walls
Ælfthryth
Æthelberht II of East Anglia
beheaded
1426day.year
King Mohnyin Thado formally ascends to the throne of Ava.
Mohnyin Thado is crowned king of the Ava Kingdom, initiating a period of consolidation in Upper Burma.
On May 20, 1426, Mohnyin Thado was formally enthroned as king of Ava after defeating rival factions. His rise followed a series of campaigns that reunited the fragmented Burmese states. Thado’s reign focused on centralizing authority, improving administrative structures, and reviving Buddhist scholarship. He promoted trade along inland routes and supported the arts. His leadership set the stage for Ava’s emergence as a regional power in the 15th century.
1426
Mohnyin Thado
throne of Ava
1775day.year
The Mecklenburg Declaration of Independence is allegedly signed in Charlotte, North Carolina.
The Mecklenburg Declaration of Independence was allegedly signed on May 20, 1775, declaring independence from British rule in Charlotte, North Carolina.
Local tradition holds that on May 20, 1775, leaders in Mecklenburg County, North Carolina, signed a Declaration of Independence from Great Britain.
If authentic, this document would predate the Continental Congress’s declaration by over a year, yet no original copy survives.
Historians debate its existence, suggesting it may have been conflated with later Mecklenburg resolutions dated 1776.
Despite the controversy, the declaration became a symbol of revolutionary fervor in North Carolina.
Today, Mecklenburg Day is observed as a state holiday, celebrating local claims to early American independence.
The mystery of the Mecklenburg Declaration underscores the complexities of Revolutionary-era record-keeping.
1775
Mecklenburg Declaration of Independence
Charlotte, North Carolina
1802day.year
By the Law of 20 May 1802, Napoleon Bonaparte reinstates slavery in the French colonies, revoking its abolition in the French Revolution.
Napoleon Bonaparte’s Law of 20 May 1802 reinstated slavery in French colonies, reversing its abolition during the Revolution.
On May 20, 1802, First Consul Napoleon Bonaparte decreed the restoration of slavery in all French colonial territories, nullifying its 1794 abolition.
The decision was influenced by economic pressures from colonial planters in Guadeloupe, Martinique, and other islands.
Thousands of freed individuals were forced back into servitude under harsh conditions and colonial codes.
The law sparked resistance and uprisings, notably the 1802 revolt in Guadeloupe led by Victor Hugues.
International observers condemned the measure as a betrayal of revolutionary ideals of liberty and equality.
Slavery in French colonies would not be finally abolished again until 1848, leaving a lasting legacy on colonial societies.
1802
Law of 20 May 1802
Napoleon Bonaparte
slavery
French colonies
French Revolution
1862day.year
U.S. President Abraham Lincoln signs the Homestead Act into law, opening eighty-four million acres (340,000 km) of public land to settlers.
Abraham Lincoln signs the Homestead Act, opening 84 million acres of public land to settlers in the American West.
On May 20, 1862, President Abraham Lincoln enacted the Homestead Act to accelerate settlement of western territories. The law granted 160 acres of public land to any adult citizen or intended citizen willing to cultivate it for five years. This bold policy encouraged migration, farming, and development across the Great Plains. By offering opportunities to men and women from diverse backgrounds, the act aimed to expand the nation’s frontier. Over the next decades, millions benefited from this legislation, shaping the social and economic landscape of the American West.
1862
Abraham Lincoln
Homestead Act
1875day.year
Signing of the Metre Convention by 17 nations leading to the establishment of the International System of Units.
Seventeen nations sign the Metre Convention, establishing the framework for the International System of Units.
On May 20, 1875, seventeen nations convened in Paris and signed the Metre Convention, establishing an international framework for uniform measurement. The treaty created the International Bureau of Weights and Measures to oversee standardized units and scientific cooperation. It laid the groundwork for the metric system’s global adoption, promoting accuracy in commerce, industry, and research. Member countries agreed to base their measurements on physical prototypes and shared reference standards. The Metre Convention remains a cornerstone of international collaboration in science and engineering.
1875
Metre Convention
International System of Units
1882day.year
The Triple Alliance between the German Empire, Austria-Hungary and the Kingdom of Italy is formed.
The Triple Alliance is formed between the German Empire, Austria-Hungary, and Italy, reshaping European alliances.
On May 20, 1882, Germany, Austria-Hungary, and Italy formalized the Triple Alliance, a secret military pact aimed at defending mutual interests in Europe. Each member pledged support in the event of an attack by two or more powers or an unprovoked attack by France. The agreement shifted the balance of power on the continent and heightened tensions leading up to World War I. Though primarily defensive, it also served as a deterrent against potential aggressors. The alliance endured until Italy left the pact in 1915 amidst changing wartime pressures.
1882
Triple Alliance
Austria-Hungary
Kingdom of Italy
1902day.year
Cuba gains independence from the United States. Tomás Estrada Palma becomes the country's first President.
On May 20, 1902, Cuba officially gained independence from the United States, inaugurating Tomás Estrada Palma as its first President.
After nearly four years of U.S. military occupation following the Spanish-American War, Cuba achieved formal independence under the terms of the Platt Amendment. On this day, Tomás Estrada Palma was sworn in as the new republic's first President in Havana, symbolizing a new era of self-governance. The young nation soon faced the challenges of building political institutions and balancing U.S. influence with domestic aspirations. The establishment of the Cuban Constitution laid the groundwork for civil liberties, though debates over American involvement continued. This milestone marked the beginning of Cuba's journey as an independent state in the global community.
1902
Cuba
Tomás Estrada Palma
1927day.year
Treaty of Jeddah: The United Kingdom recognizes the sovereignty of King Ibn Saud in the Kingdoms of Hejaz and Nejd, which later merge to become the Kingdom of Saudi Arabia.
On May 20, 1927, the United Kingdom formally recognized King Ibn Saud's sovereignty over Hejaz and Nejd through the Treaty of Jeddah, paving the way for the future Kingdom of Saudi Arabia.
The Treaty of Jeddah marked the end of British protectorate status for the Hejaz and Nejd regions after Ibn Saud's military campaigns. By recognizing his rule, Britain acknowledged the consolidation of power under the Saudi House of Saud. This diplomatic milestone reduced foreign interference and bolstered Ibn Saud's legitimacy on the international stage. With newfound recognition, the two kingdoms unified five years later to form the Kingdom of Saudi Arabia. The agreement also set the stage for future oil concessions and geopolitical alliances in the Middle East.
1927
Treaty of Jeddah
sovereignty
Ibn Saud
Hejaz
Nejd
Saudi Arabia
1948day.year
Generalissimo Chiang Kai-shek wins the 1948 Republic of China presidential election and is sworn in as the first President of the Republic of China at Nanjing.
On May 20, 1948, Chiang Kai-shek was inaugurated as the first President of the Republic of China following his victory in the nation's inaugural presidential election.
Held under the 1947 Constitution, the 1948 election marked the Republic of China's transition to constitutional governance. Chiang Kai-shek and his Kuomintang party maintained tight control, securing his presidency amid the ongoing Chinese Civil War. His inauguration in Nanjing symbolized the government's attempt to legitimize its authority against Communist forces. Despite constitutional promises, martial law and party dominance limited political freedoms. The conflict with Mao Zedong's forces intensified, ultimately leading to the ROC government's retreat to Taiwan in 1949.
1948
Chiang Kai-shek
1948 Republic of China presidential election
President of the Republic of China
Nanjing