Convert Synodic Months to Tropical Years
Convert Synodic Months (syn.mo) to Tropical Years (a_trop) instantly and accurately.
Conversion Formula
a_trop = syn.mo × 0.08085207476
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.
About Tropical Years
The tropical year = time from March equinox to the next = 365.24219 days = 31,556,925.2 s - the year that governs the seasons. The Gregorian 97/400 leap rule approximates it as 365.2425 days, leaving a residual drift of only ~26.8 s/year. The tropical year shortens ~0.53 s per century due to tidal deceleration. Persian Solar Hijri and Mayan Haab' calendars also approximate it. 1 a_trop ≈ 365.24219 d.
Quick Reference Table
| Synodic Months (syn.mo) | Tropical Years (a_trop) |
|---|---|
| 1 syn.mo | 0.0808521 a_trop |
| 2 syn.mo | 0.161704 a_trop |
| 5 syn.mo | 0.40426 a_trop |
| 10 syn.mo | 0.808521 a_trop |
| 25 syn.mo | 2.0213 a_trop |
| 50 syn.mo | 4.0426 a_trop |
| 100 syn.mo | 8.08521 a_trop |