We tend to think of the Roman Empire as an entirely ancient time period. Yet while the Western Roman Empire fell in the fifth century CE, leaving it firmly in the ancient world, the eastern half of the empire kept going for another millennium — as late as 1453. Emperor Diocletian divided Rome at the end of the third century BCE, believing the empire had become too big to be ruled by just one monarch. The western half encompassed Europe and Northern Africa, and the eastern half covered the Middle East. As the west faltered, the east stayed strong, largely thanks to in-demand exports such as spices. In 395 CE, the Eastern Roman Empire split off entirely, and it eventually even took back some former Western Roman territory.

Historians often refer to the Eastern Roman Empire as the Byzantine Empire, but that term wasn’t used until after it fell; the citizens of the empire still thought of themselves as Romaioi, or Romans. The capital was Constantinople (now Istanbul in modern-day Turkey), named after Emperor Constantine I. As Constantine was the first Christian emperor of Rome, the Byzantines adopted Christianity as the state religion. But they also embraced their heritage from ancient Greece, and in the seventh century CE, Greek replaced Latin as the empire’s official language. 

In the 11th century CE, the Byzantine Empire faced escalating threats from both sides — the Crusades caused tension with Western Europe, and the Turks destabilized Anatolia, the point where Asia meets Europe. The empire fell in 1453 when Ottoman Turks breached the walls of Constantinople after a 55-day siege, toppling the last vestiges of the long-powerful Roman Empire. By then, Europe was in the early stages of the Renaissance and the Age of Exploration. Christopher Columbus set sail to the Americas in 1492, just 39 years later.

Septuplets are seven siblings born at the same time; a septennium is a period of seven years; and September is the… ninth month of the year. What gives? As you may expect, “sept” is a prefix with Latin roots that means “seven,” and it didn’t end up at the beginning of the word “September” by accident.

The month of September was originally part of the Roman republican calendar, which was used in ancient Rome for hundreds of years before the debut of the Julian calendar in 46 BCE. At first, the Roman republican calendar included just 10 months. The last six months all corresponded to their Latin numbers, which is how not just September but also October (meaning “eighth”), November (“ninth”), and December (“tenth”) all got their names. (The fifth month, Quintilis, and the sixth month, Sextilis, were later renamed after Roman rulers.)

January and February joined the calendar later as the first and last month, respectively, but nobody changed September’s name, despite it quite literally meaning “seventh” for the Latin speakers in ancient Rome. The name stuck even after February shifted to second in order in 452 BCE, meaning that September has been the ninth month for much longer than it was ever the seventh month of the year.