Why Does February Only Have 28 Days? the 2,000-Year-Old Roman Superstition Explained
Numa’s 355-day lunar year was flawed. Because a solar year lasts roughly 365.24 days, the Roman calendar drifted away from the natural seasons by roughly 10 days every year. To reconcile the difference, the College of Pontiffs was tasked with inserting an intercalary month called Mercedonius (measuring 27 days) every two or three years.
The insertion of Mercedonius was corrupt. Roman politicians routinely extended years when allies held power or skipped intercalations when rivals were in office. By 46 BCE, the civil calendar was nearly three months out of sync with astronomical seasons. Harvest festivals fell in early summer, and spring celebrations took place during midwinter.
Julius Caesar intervened. Advised by the Alexandrian astronomer Sosigenes, Caesar severed ties with the moon and tied the state calendar strictly to the solar year. In 46 BCE, known to historians as the "Year of Confusion," which lasted 445 days to reset seasonal alignment, Caesar established a 365-day year. He distributed 10 extra days across the months that had previously held 29 days, boosting them to 30 or 31.
Caesar left February at its ancient 28-day baseline. Rather than artificially inflating February to match the others, he used the month as the designated release valve for the remaining solar fraction. Every four years, an intercalary day was added to February, creating the formal leap year cycle. A persistent popular myth claims Augustus Caesar later stole a day from February to add to August so his namesake month would match Julius Caesar's July. Classical Roman records prove this narrative false; August had 31 days from the moment Caesar established the Julian reform.
