Convert Year (Julian) (y (Julian)) to Second (s) instantly.
About these units
Year (Julian) (y (Julian))
A Julian year is defined as exactly 365.25 days, reflecting the structure of the Julian calendar introduced by Julius Caesar in 45 BCE. This calendar assumed a fixed year length with a leap year every four years. Although revolutionary in its simplicity, the Julian year overestimates the actual tropical year by about 11 minutes, causing the calendar date to drift slowly relative to the seasons—an issue that accumulated to more than 10 days by the 16th century. Astronomers still use the Julian year as a standardized unit for long-term timekeeping, especially when expressing stellar motions, orbital periods, and cosmological timescales. Its simplicity and fixed length make it ideal for scientific definition even though it is obsolete as a civil calendar.
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.