A leap year is a year that is divisible by four, with the exception of years that are divisible by 100 unless they are also divisible by 400, to synchronize the calendar year with the astronomical year. This adjustment compensates for the fact that a solar year is approximately 365.2425 days long, preventing calendar drift over time.

Leap Year

leap year

divisible by four

exception of years

divisible by 100

divisible by 400

synchronize the calendar year

An astronomical year, also known as a sidereal year, is the time it takes for Earth to complete one orbit around the Sun relative to fixed stars, approximately 365.25636 days. This period is slightly longer than a calendar year due to Earth's axial precession and orbital dynamics, affecting the alignment of seasons over millennia.

astronomical year

Calendar drift refers to the gradual misalignment of calendar dates with astronomical or seasonal events due to an imprecise definition of a year's length within the calendar system. This drift necessitates periodic adjustments, like leap years in the Gregorian calendar, to realign calendars with the Earth's position in its orbit around the Sun.

calendar drift

A solar year, also known as a tropical year, is the time it takes for the Earth to complete one orbit around the Sun, measured relative to the equinoxes, averaging about 365.242 days. This period is fundamental to the Gregorian calendar, which is designed to align with the solar year to ensure seasonal consistency over long periods.

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