Day

Definition

A day is a unit of time traditionally defined as the duration of one complete rotation of the Earth on its axis. In the International System of Units (SI), it is not a base unit but is widely accepted as a standard time measure. The canonical definition is 86,400 seconds.

History

The concept of a day has ancient roots, dating back to early civilizations like the Egyptians and Babylonians, who divided the day into two 12-hour periods. The 24-hour day was formalized by the Greeks and was adopted globally. The introduction of the atomic clock in the 20th century led to a more precise measurement of time, solidifying the definition of a day in modern contexts.

Uses

Days are used universally in everyday life to measure time. In science and engineering, they serve as a basic unit in various calculations, such as project timelines and experiments. Many cultures observe days through calendars, marking significant events.

Conversions

• 1 day = 24 hours
• 1 day = 1,440 minutes
• 1 day = 86,400 seconds

Fun Facts

• A "solar day" is based on the Earth's position relative to the Sun, while a "sidereal day" measures a full rotation relative to distant stars, lasting about 23 hours, 56 minutes, and 4 seconds.
• Leap years add an extra day (February 29) to correct discrepancies in the calendar year.