Solar year

The interval for Earth to return to the same seasonal position in its orbit, averaging about 365.2422 days. It is also called the tropical year.

Axial tilt: The angle between a body's rotational axis and the perpendicular to its orbital plane. Earth’s tilt makes its changing orbital position produce the annual cycle of seasons.
Sidereal year: The time Earth takes to complete one orbit relative to the distant stars, about 365.256 days. It tracks the stars, while the solar year tracks the seasonal cycle.
Metonic cycle: A period of 19 years after which lunar phases recur on nearly the same calendar dates. It helped ancient calendars reconcile lunar months with the seasonal year.
Leap year: A calendar year containing an extra day or month to keep its dates aligned with an astronomical cycle. Leap days compensate for the seasonal year’s fraction beyond 365 days.
Earth's orbit: The path Earth follows around the Sun, an ellipse with the Sun at one focus. The orbital motion that carries Earth through successive seasonal positions.
Anomalistic year: The interval between successive passages of Earth through perihelion, about 365.259 days. Its perihelion reference differs from the seasonal reference of the solar year.
Egyptian calendar: An ancient civil calendar of twelve 30-day months plus five additional days, totaling 365 days. Its shortfall against the seasonal year caused its dates to drift through the seasons.
Tropical calendar: A calendar designed to keep months and dates aligned with the seasons. Its year length is chosen to track the seasonal cycle.
Equinox: An instant when the Sun crosses Earth's celestial equator, producing nearly equal day and night. The vernal equinox is a reference point for measuring the seasonal cycle.
Draconic year: The interval between successive passages of the Sun through the same lunar orbital node, about 346.62 days. It is defined by lunar eclipse geometry, not Earth's return to a season.

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