Convert Sidereal Years to Fortnights
Convert Sidereal Years (a_sid) to Fortnights (fn) instantly and accurately.
Conversion Formula
fn = a_sid × 26.08974021
About Sidereal Years
The sidereal year = Earth's orbital period relative to the stars = 365.25636 days = 31,558,149.8 s - about 20 min 24 s longer than the tropical year. The gap arises from precession of the equinoxes (~50 arcsec/year westward drift), which causes the tropical year to end slightly before the sidereal orbit completes. JPL DE440 ephemerides and J2000.0 epoch are anchored to the sidereal frame. 1 a_sid = 365.25636 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
| Sidereal Years (a_sid) | Fortnights (fn) |
|---|---|
| 1 a_sid | 26.0897 fn |
| 2 a_sid | 52.1795 fn |
| 5 a_sid | 130.449 fn |
| 10 a_sid | 260.897 fn |
| 25 a_sid | 652.244 fn |
| 50 a_sid | 1304.49 fn |
| 100 a_sid | 2608.97 fn |