Misplaced Pages

This is an old revision of this page, as edited by 2a02:a44f:c097:1:68df:cc9b:c1f1:2ff4 (talk) at 17:36, 17 October 2023 (→Analogs in other languages). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

A fortnight is a unit of time equal to 14 days (two weeks). The word derives from the Old English term fēowertīene niht, meaning "fourteen nights" (or "fourteen days", since the Anglo-Saxons counted by nights).

Astronomy and tides

In astronomy, a lunar fortnight is half a lunar synodic month, which is equivalent to the mean period between a full moon and a new moon (and vice versa). This is equal to 14.07 days. It gives rise to a lunar fortnightly tidal constituent (see: Long-period tides).

boo

See also

• FFF system
• Half-month
• Sennight

References

1. "Fortnight". The Concise Oxford Dictionary (5th ed.). 1964. p. 480.
2. Senight, sennight or se'night (seven-night), an old word for the week, was still in use in the early 19th century, to judge from Jane Austen's letters.
3. Littmann, Mark; Fred Espenak; Ken Willcox (2008). Totality: Eclipses of the Sun. Oxford University Press. ISBN 978-0-19-953209-4.
4. Weisstein, Eric W. "Synodic Month definition".

v t e Time measurement and standards
Chronometry Orders of magnitude Metrology
International standards	Coordinated Universal Time offset UT ΔT DUT1 International Earth Rotation and Reference Systems Service ISO 31-1 ISO 8601 International Atomic Time 12-hour clock 24-hour clock Barycentric Coordinate Time Barycentric Dynamical Time Civil time Daylight saving time Geocentric Coordinate Time International Date Line IERS Reference Meridian Leap second Solar time Terrestrial Time Time zone 180th meridian
Obsolete standards	Ephemeris time Greenwich Mean Time Prime meridian
Time in physics	Absolute space and time Spacetime Chronon Continuous signal Coordinate time Cosmological decade Discrete time and continuous time Proper time Theory of relativity Time dilation Gravitational time dilation Time domain Time-translation symmetry T-symmetry
Horology	Clock Astrarium Atomic clock Complication History of timekeeping devices Hourglass Marine chronometer Marine sandglass Radio clock Watch stopwatch Water clock Sundial Dialing scales Equation of time History of sundials Sundial markup schema
Calendar	Gregorian Hebrew Hindu Holocene Islamic (lunar Hijri) Julian Solar Hijri Astronomical Dominical letter Epact Equinox Intercalation Julian day Leap year Lunar Lunisolar Solar Solstice Tropical year Weekday determination Weekday names
Archaeology and geology	Chronological dating Geologic time scale International Commission on Stratigraphy
Astronomical chronology	Galactic year Nuclear timescale Precession Sidereal time
Other units of time	Instant Flick Shake Jiffy Second Minute Moment Hour Day Week Fortnight Month Year Olympiad Lustrum Decade Century Saeculum Millennium
Related topics	Chronology Duration music Mental chronometry Decimal time Metric time System time Time metrology Time value of money Timekeeper

• Units of time