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.
astronomer
Noun

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

define
Verb

to identify or associate with.

Noun

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

Julius Caesar
Noun

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

revolve
Verb

to orbit or spin around something.

Noun

period of the year distinguished by special climatic conditions.

sun
Noun

star at the center of our solar system.

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February
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28 29 30 31 1 2 3
4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 1 2 3
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