Convert Year (Julian) (y (Julian)) to Second (Sidereal) (s (sidereal)) 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 Its simplicity and fixed length make it ideal for scientific definition even though it is obsolete as a civil calendar.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 (Sidereal) (s (sidereal))
A sidereal second is 1/60 of a sidereal minute, equal to about 0.99727 solar seconds. While the difference seems small, it accumulates noticeably over long observing sessions. Sidereal seconds ensure that telescope mounts and tracking systems remain synchronized with the rotation of the celestial sphere. The distinction between solar and sidereal seconds underscores the complexity of Earth's rotational dynamics—reminding us that even "one second" depends on which cosmic frame of reference we choose.