Convert Sidereal Years to Days
Convert Sidereal Years (a_sid) to Days (d) instantly and accurately.
Conversion Formula
d = a_sid × 365.256363
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 Days
A day (d) = exactly 86,400 s. Earth's actual solar day varies ±16 s due to orbital eccentricity and axial tilt (equation of time). Leap seconds (abandoned in UTC after 2035) corrected the TAI-UT1 divergence. Mars's sol = 24 h 39 min 35 s ≈ 88,775 s; a Martian year = 668.6 sols. The day structures circadian biology, tides, and planetary science. 1 day = 86,400 s = 24 h.
Quick Reference Table
| Sidereal Years (a_sid) | Days (d) |
|---|---|
| 1 a_sid | 365.256 d |
| 2 a_sid | 730.513 d |
| 5 a_sid | 1826.28 d |
| 10 a_sid | 3652.56 d |
| 25 a_sid | 9131.41 d |
| 50 a_sid | 18262.8 d |
| 100 a_sid | 36525.6 d |