Why is the ninth month called September?
c.1050, Iulius, from Anglo-French julie, Old French Jule, from Latin Iulius "fifth month of the Roman calendar" (which began its year in March), renamed after his death and deification in honor of Gaius Julius Caesar, who was born in this month, which formerly in republican Rome was named Quintilis "fifth." Accented on first syllable in English until 18c. Replaced Old English liða se æfterra "later mildness," from liðe "mild."
seventh month of the Gregorian calendar. It was named after Julius Caesar in 44 BCE. Its original name was Quintilis, Latin for the "fifth month," indicating its position in the early Roman calendar.