Convert Fortnights to Synodic Months
Convert Fortnights (fn) to Synodic Months (syn.mo) instantly and accurately.
Conversion Formula
syn.mo = fn × 0.4740846879
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.
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
| Fortnights (fn) | Synodic Months (syn.mo) |
|---|---|
| 1 fn | 0.474085 syn.mo |
| 2 fn | 0.948169 syn.mo |
| 5 fn | 2.37042 syn.mo |
| 10 fn | 4.74085 syn.mo |
| 25 fn | 11.8521 syn.mo |
| 50 fn | 23.7042 syn.mo |
| 100 fn | 47.4085 syn.mo |