Convert Millennia to Sidereal Years
Convert Millennia (ka) to Sidereal Years (a_sid) instantly and accurately.
Conversion Formula
a_sid = ka × 999.9620458
About Millennia
A millennium (1 ka) = 1,000 Gregorian years ≈ 3.156 × 10¹⁰ s. Standard unit in archaeology and Quaternary geology: Neolithic transition ~10-12 ka BP; Last Glacial Maximum ~21 ka BP; Homo sapiens leaving Africa ~60-70 ka BP. Milankovitch cycles include the 41 ka obliquity and ~100 ka eccentricity cycle. EPICA Antarctic ice core spans ~800 ka. Precession completes ~26 ka. 1 ka = 1,000 yr.
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.
Quick Reference Table
| Millennia (ka) | Sidereal Years (a_sid) |
|---|---|
| 1 ka | 999.962 a_sid |
| 2 ka | 1999.92 a_sid |
| 5 ka | 4999.81 a_sid |
| 10 ka | 9999.62 a_sid |
| 25 ka | 24999.1 a_sid |
| 50 ka | 49998.1 a_sid |
| 100 ka | 99996.2 a_sid |