Convert Second (s) to Year (Sidereal) (y (sidereal)) instantly.
About these units
Second (s)
The second is the fundamental SI unit of time and the basis for nearly every modern timing system, from everyday clocks to astronomical calculations and quantum physics. Historically, the second was defined as 1/86,400 of a mean solar day—reflecting Earth's rotation. But because Earth's rotation is not perfectly constant, this definition proved insufficient for scientific precision. Today, the second is defined by the vibration frequency of the cesium-133 atom, specifically 9,192,631,770 oscillations of its hyperfine transition. This atomic definition gives the second extraordinary accuracy and stability, enabling technologies like GPS, satellite communications, deep-space navigation, and particle physics experiments. The second sits at the intersection of human history and cutting-edge physics: once tied to the apparent motion of the Sun, it is now anchored to a universal atomic constant, making it one of the most precisely defined units in science.
Year (Sidereal) (y (sidereal))
A sidereal year is the time it takes Earth to complete one full orbit relative to distant fixed stars, lasting approximately 365.25636 days. This is the "true" orbital period of Earth in space, unaffected by precession-related shifts of the equinoxes. Sidereal years are used in celestial mechanics, spacecraft navigation, and modeling solar system dynamics. The slight difference between the tropical and sidereal year (about 20 minutes) reveals how Earth's wobbling axis alters how we perceive time, creating two distinct astronomical year definitions.