May 29

Roman Emperor Julian defeats a Sasanian army near Ctesiphon but is unable to capture the Persian capital.

Roman Emperor Julian, known as "the Apostate" for his rejection of Christianity, led his forces to a tactical victory over a defending Sasanian Persian army near the fortified capital of Ctesiphon, though he ultimately proved unable to breach the city's formidable defenses, complicating and ultimately dooming the broader campaign's strategic objectives.

The Lombard League defeats Holy Roman Emperor Frederick I at the Battle of Legnano, checking his ambitions in northern Italy.

The Lombard League, a defensive alliance of northern Italian city-states banded together against imperial encroachment, decisively defeated the army of Holy Roman Emperor Frederick I "Barbarossa" at the Battle of Legnano, checking his ambitions in Italy and preserving significant local political autonomy for the fiercely independent Italian communes.

Ottoman forces under Sultan Mehmed II capture Constantinople, ending the more than thousand-year-old Byzantine Empire.

Ottoman forces under the young Sultan Mehmed II finally breached the ancient walls of Constantinople after a grueling fifty-three-day siege employing massive new siege cannons, bringing a definitive end to the more than thousand-year-old Byzantine Empire and establishing the city as the new capital of the expanding Ottoman Empire.

Charles II is restored to the thrones of England, Scotland, and Ireland, ending the English Interregnum.

Charles II was restored to the thrones of England, Scotland, and Ireland, entering London in triumph to widespread public celebration on his thirtieth birthday, ending the eleven-year republican Interregnum and Commonwealth period that had followed his father Charles I's execution.

Rhode Island becomes the last of the original thirteen colonies to ratify the U.S. Constitution.

Rhode Island became the last of the original thirteen American states to ratify the U.S. Constitution, having initially resisted for years due to deep concerns about excessive centralized federal power and the notable absence of an explicit bill of rights protecting individual liberties.

Sojourner Truth delivers her celebrated "Ain't I a Woman?" speech at a women's rights convention in Ohio.

Formerly enslaved abolitionist and women's rights activist Sojourner Truth delivered her powerful, extemporaneous "Ain't I a Woman?" speech at a women's rights convention in Akron, Ohio, an address later widely reprinted and celebrated as a foundational text of American feminist and civil rights history.

John Pemberton places the first newspaper advertisement for Coca-Cola in The Atlanta Journal.

Pharmacist John Pemberton placed the first newspaper advertisement for his new caramel-colored beverage, Coca-Cola, in The Atlanta Journal, describing it as "delicious and refreshing," an early promotional step in what would grow into one of the most recognized and valuable consumer brands in the world.

Astronomer Arthur Eddington's observations of a solar eclipse provide the first experimental confirmation of Einstein's theory of general relativity.

British astronomer Arthur Eddington's carefully coordinated observations of star positions during a total solar eclipse visible from the island of Príncipe provided the first experimental evidence confirming Albert Einstein's theory of general relativity, transforming Einstein into an international scientific celebrity almost overnight.

Edmund Hillary and Tenzing Norgay become the first climbers confirmed to reach the summit of Mount Everest.

New Zealand mountaineer Edmund Hillary and Nepalese Sherpa mountaineer Tenzing Norgay became the first climbers officially confirmed to reach the summit of Mount Everest, the world's highest peak, achieving what was long considered one of the last great remaining feats of human physical exploration on Earth.

Pope John Paul II becomes the first pontiff to visit Canterbury Cathedral, a significant moment in Catholic-Anglican relations.

Pope John Paul II became the first Roman pontiff to visit Canterbury Cathedral, the historic seat of the Anglican Communion, praying together with the Archbishop of Canterbury in a symbolically significant gesture within the long, gradual process of reconciliation between the Catholic and Anglican churches following centuries of division.