päiväntasauksen
Päiväntasauksen refers to the equinox in Finnish. An equinox is an astronomical event that occurs twice each year, when the Sun is directly above the Earth's equator. During an equinox, the day and night are of approximately equal length across most of the planet. The term "equinox" comes from the Latin words "aequus" meaning equal, and "nox" meaning night. There are two equinoxes: the vernal equinox, which typically occurs around March 20th or 21st, marking the beginning of spring in the Northern Hemisphere and autumn in the Southern Hemisphere, and the autumnal equinox, which usually falls on September 22nd or 23rd, signaling the start of autumn in the Northern Hemisphere and spring in the Southern Hemisphere. The precise timing of the equinoxes varies slightly each year due to the Earth's elliptical orbit and the Gregorian calendar's leap year system. On the equinox, the tilt of the Earth's axis is neither away from nor towards the Sun. This alignment results in the Sun rising due east and setting due west everywhere on Earth, simplifying celestial observations.