Päikesekalendrite

Päikesekalendrite is a term that refers to solar calendars. These are timekeeping systems where the passage of time is measured by the position of the Earth in its orbit around the Sun. The most common and widely used solar calendar today is the Gregorian calendar, which is based on the tropical year, the time it takes for the Earth to complete one orbit around the Sun relative to the vernal equinox.

The fundamental principle of a solar calendar is to align the calendar year with the solar year. This is crucial for keeping seasons consistent with calendar dates. Early solar calendars were often developed by ancient civilizations to track agricultural cycles and religious festivals tied to celestial events. For example, the ancient Egyptians developed a solar calendar that was remarkably accurate for its time, based on the heliacal rising of the star Sirius, which coincided with the annual flooding of the Nile River.

While the Gregorian calendar is the dominant solar calendar globally, other solar or lunisolar calendars exist or have existed historically. Lunisolar calendars attempt to synchronize both lunar cycles and the solar year, often by adding intercalary months. However, pure solar calendars, like the Gregorian, prioritize the solar year. The accuracy of solar calendars is maintained through a system of rules, including the use of leap years, to account for the fact that the solar year is not an exact whole number of days. This ensures that the calendar remains synchronized with the Earth's orbital period over long stretches of time.