Convert Gregorian Years to Synodic Months
Convert Gregorian Years (yr) to Synodic Months (syn.mo) instantly and accurately.
Conversion Formula
syn.mo = yr × 12.3682769
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 Synodic Months
A synodic (lunar) month = new moon to new moon = 29.5306 days = 2,551,442.9 s. Longer than the sidereal month (27.32 d) because Earth advances ~27° in its orbit during that time; the Moon must travel further to realign with the Sun. Islamic Hijri, Hebrew lunisolar, and Chinese calendars are built on synodic months. Eclipses repeat via the Saros cycle (18 yr 11 d = 223 synodic months). 1 syn.mo ≈ 29.5306 d.
Quick Reference Table
| Gregorian Years (yr) | Synodic Months (syn.mo) |
|---|---|
| 1 yr | 12.3683 syn.mo |
| 2 yr | 24.7366 syn.mo |
| 5 yr | 61.8414 syn.mo |
| 10 yr | 123.683 syn.mo |
| 25 yr | 309.207 syn.mo |
| 50 yr | 618.414 syn.mo |
| 100 yr | 1236.83 syn.mo |