Convert Gregorian Years to Millennia
Convert Gregorian Years (yr) to Millennia (ka) instantly and accurately.
Conversion Formula
ka = yr × 0.001
About Gregorian Years
The Gregorian year = exactly 365.2425 days = 31,556,952 s (mean over the 400-year cycle with 97 leap years). The Julian calendar (45 BCE) used 365.25 days; Gregorian reform (1582) dropped 10 days and amended the centennial rule. Britain adopted it in 1752; Greece in 1923. Carbon-14 dates are reported in 'years BP' (before 1950 CE). 1 yr = 365.2425 d = 8,765.82 h = 31,556,952 s.
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.
Quick Reference Table
| Gregorian Years (yr) | Millennia (ka) |
|---|---|
| 1 yr | 0.001 ka |
| 2 yr | 0.002 ka |
| 5 yr | 0.005 ka |
| 10 yr | 0.01 ka |
| 25 yr | 0.025 ka |
| 50 yr | 0.05 ka |
| 100 yr | 0.1 ka |