Convert Synodic Months to Fortnights
Convert Synodic Months (syn.mo) to Fortnights (fn) instantly and accurately.
Conversion Formula
fn = syn.mo × 2.109327775
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 Fortnights
A fortnight = exactly 14 days = 2 weeks = 1,209,600 s. From Old English 'feowertiene niht' (fourteen nights), reflecting the Germanic custom of counting nights. Common in British, Irish, Australian, and NZ English for pay periods, rental cycles, and parliamentary recesses. The Moon's phase advances ~half a synodic month (≤14.77 days) per fortnight; spring and neap tides also cycle fortnightly. 1 fortnight = 14 d = 1,209,600 s.
Quick Reference Table
| Synodic Months (syn.mo) | Fortnights (fn) |
|---|---|
| 1 syn.mo | 2.10933 fn |
| 2 syn.mo | 4.21866 fn |
| 5 syn.mo | 10.5466 fn |
| 10 syn.mo | 21.0933 fn |
| 25 syn.mo | 52.7332 fn |
| 50 syn.mo | 105.466 fn |
| 100 syn.mo | 210.933 fn |