Convert Sidereal Years to Julian Years
Convert Sidereal Years (a_sid) to Julian Years (a_J) instantly and accurately.
Conversion Formula
a_J = a_sid × 1.000017421
About Sidereal Years
The sidereal year = Earth's orbital period relative to the stars = 365.25636 days = 31,558,149.8 s - about 20 min 24 s longer than the tropical year. The gap arises from precession of the equinoxes (~50 arcsec/year westward drift), which causes the tropical year to end slightly before the sidereal orbit completes. JPL DE440 ephemerides and J2000.0 epoch are anchored to the sidereal frame. 1 a_sid = 365.25636 d.
About Julian Years
The Julian year (a_J) = exactly 365.25 days = 31,557,600 s - the IAU standard year for astronomical distances. The light-year is formally 1 ly = c × 1 a_J = 9.461 × 10¹⁵ m (IAU 2012 B2). Julian years differ from Gregorian years by only 648 s (~10.8 min/year); important for high-precision astrometry or calculations spanning centuries. 1 a_J = 365.25 d = 31,557,600 s.
Quick Reference Table
| Sidereal Years (a_sid) | Julian Years (a_J) |
|---|---|
| 1 a_sid | 1.00002 a_J |
| 2 a_sid | 2.00003 a_J |
| 5 a_sid | 5.00009 a_J |
| 10 a_sid | 10.0002 a_J |
| 25 a_sid | 25.0004 a_J |
| 50 a_sid | 50.0009 a_J |
| 100 a_sid | 100.002 a_J |