Gregorian calendar

Introduction & Top Questions References & Edit History Quick Facts & Related Topics

Images, Videos & Interactives

Stone relief on Pope Gregory XIII's tomb in Saint Peter's Basilica, showing the pope seated among clergy as a figure presents a document and another gestures to a globe.

What Is Leap Day?

Interactive Gregorian calendar tool with fields for year, month, day, and era, set to December 8, 2025, and a blue Calculate button at the bottom.

Gregorian calendar: Media

dating system

Videos

What Is Leap Day?

What Is Leap Day?

An extra day is added to the calendar about every four years. Why?

Video: Encyclopædia Britannica, Inc.

Images

Stone relief on Pope Gregory XIII's tomb in Saint Peter's Basilica, showing the pope seated among clergy as a figure presents a document and another gestures to a globe.

Gregorian calendar

The introduction of the Gregorian calendar, depicted in relief on the tomb of Pope...

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Interactives

Interactive Gregorian calendar tool with fields for year, month, day, and era, set to December 8, 2025, and a blue Calculate button at the bottom.

Calendar conversion

Encyclopædia Britannica, Inc.

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