Tropical year

Article

A tropical year is the time required for the Sun to return to the same position in the seasonal cycle, such as from one vernal equinox to the next. Its mean length is approximately 365.24219 days.

It is shorter than the sidereal year because axial precession moves the equinoxes westward while Earth travels around the Sun. Earth therefore reaches the next seasonal reference point before completing a full orbit relative to the stars.

The tropical year is fundamental to solar calendars because it keeps calendar dates aligned with the seasons. Leap-year rules approximate its fractional number of days.

The exact interval between particular equinoxes or solstices varies slightly because Earth's orbital speed is not constant and because the orbit and rotational axis are continually perturbed.

Source details and credits

• Source / publisher: Wikipedia
• URL type: WWW
• Credits: Wikipedia
• URL: https://en.wikipedia.org/wiki/Tropical_year