Julius Caesar was probably ancient Rome's most famous military commander and political leader. His administration also reformed the calendar.

Photograph by James L. Stanfield, National Geographic
  • On February 29, 45 BCE, the first Leap Day was added to the calendar. Roman leader Julius Caesar was worried about how the calendar kept falling out of step with the seasons. Egyptian astronomers told him that the year, defined by how long it takes Earth to revolve around the sun, is 365.25 days long. To cover for the extra one-fourth of a day, Caesar added an extra day at the end of February every four years. 
    The “Julian calendar” was the standard for most European calendars for more than a thousand years.
  • Term Part of Speech Definition Encyclopedic Entry
    astronomer Noun

    person who studies space and the universe beyond Earth's atmosphere.

    define Verb

    to identify or associate with.

    Earth Noun

    our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

    Encyclopedic Entry: Earth
    Julius Caesar Noun

    (100 BCE-44 BCE) leader of ancient Rome.

    revolve Verb

    to orbit or spin around something.

    season Noun

    period of the year distinguished by special climatic conditions.

    Encyclopedic Entry: season
    sun Noun

    star at the center of our solar system.