Fortnight to Sidereal Day Conversion Calculator: Free Online Tool
Convert fortnights to sidereal days with our free online time converter.
Fortnight to Sidereal Day Calculator
How to Use the Calculator:
- Enter the value you want to convert in the 'From' field (Fortnight).
- The converted value in Sidereal Day will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Time category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Fortnight to Sidereal Day
Converting Fortnight to Sidereal Day involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Fortnight = 14.03833 sidereal daysExample Calculation:
Convert 60 fortnights: 60 × 14.03833 = 842.2998 sidereal days
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.
What is a Fortnight and a Sidereal Day?
A fortnight is a unit of time equal to exactly two weeks, which corresponds to 14 days or 336 hours.
A sidereal day is the time it takes for the Earth to complete one full rotation on its axis relative to the distant, fixed stars. It is approximately 23 hours, 56 minutes, and 4.091 seconds long. This is slightly shorter than the 24-hour solar day, which is based on the Earth's rotation relative to the Sun.
Note: The Fortnight is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Sidereal Day belongs to the imperial/US customary system.
History of the Fortnight and Sidereal Day
The word "fortnight" originates from the Old English term "fēowertīene niht," meaning "fourteen nights." Counting periods by nights was common among ancient Germanic peoples. The term has been in continuous use in English for centuries and remains relatively common in the United Kingdom, Ireland, Australia, New Zealand, and some other Commonwealth countries, although its usage has declined somewhat in favor of "two weeks," especially in North America.
The concept of the sidereal day originates from ancient astronomy. Early astronomers observed that the stars appeared to return to the same position in the sky slightly earlier each day when measured against the Sun's cycle. This discrepancy led to the understanding that the Earth's rotation period relative to the background stars (sidereal) was different from its rotation period relative to the Sun (solar). Accurate measurement of the sidereal day became crucial for precise astronomical observations and timekeeping, allowing astronomers to predict the positions of celestial objects.
Common Uses for fortnights and sidereal days
Explore the typical applications for both Fortnight (imperial/US) and Sidereal Day (imperial/US) to understand their common contexts.
Common Uses for fortnights
- Scheduling: Used in some regions for scheduling events, meetings, or appointments that occur every two weeks.
- Payroll: Some companies, particularly in the UK and Australia, operate on a fortnightly pay cycle (paid every two weeks).
- Publications: Certain magazines or journals might be published fortnightly (bi-weekly).
- General Conversation: Used informally in regions where the term is common to refer to a two-week period (e.g., "I'm going on holiday for a fortnight").
- Literary/Formal Contexts: Sometimes used in literature or more formal writing for stylistic reasons or historical accuracy.
Common Uses for sidereal days
The sidereal day and sidereal time are primarily used in:
- Astronomy: To point telescopes accurately at celestial objects. Astronomical observatories use sidereal clocks to know when specific stars or galaxies will be overhead or in a particular position for observation.
- Astrophysics: For calculations involving celestial mechanics and the timing of astronomical events.
- Satellite Tracking: Used in calculations for positioning and tracking artificial satellites in Earth orbit.
- Geodesy: For precise measurements related to the Earth's rotation and orientation in space.
It is generally not used for civil timekeeping, which relies on the solar day.
Frequently Asked Questions
Questions About Fortnight (fn)
How many days are in a fortnight?
A fortnight consists of exactly 14 days (or 336 hours).
How many weeks make a fortnight?
A fortnight is equal to exactly 2 weeks.
Where does the word "fortnight" come from?
It originates from the Old English phrase "fēowertīene niht," which literally translates to "fourteen nights," reflecting an old practice of counting periods of time by the number of nights.
Is "fortnight" commonly used everywhere?
No, its usage varies significantly by region. It remains relatively common in everyday language in the United Kingdom, Ireland, Australia, New Zealand, and some other Commonwealth countries. However, in North America and many other parts of the world, the term "two weeks" is far more prevalent.
About Sidereal Day (sidereal day)
How long is a sidereal day in standard time?
A mean sidereal day is approximately 23 hours, 56 minutes, and 4.091 seconds (or about 86,164.091 seconds). This is roughly 3 minutes and 56 seconds shorter than a standard 24-hour solar day.
Why is a sidereal day shorter than a solar day?
A sidereal day measures Earth's rotation relative to distant stars. A solar day measures rotation relative to the Sun. As the Earth rotates, it also orbits the Sun. After one full rotation relative to the stars (one sidereal day), the Earth has moved slightly along its orbit. It needs to rotate a little bit further (about 1 degree, taking nearly 4 minutes) to bring the Sun back to the same apparent position in the sky (completing a solar day).
Is sidereal time the same everywhere on Earth?
No, just like solar time, local sidereal time depends on your longitude. At any given moment, different locations on Earth will have different local sidereal times, corresponding to which part of the celestial sphere is currently crossing their local meridian. However, the duration of a sidereal day is the same everywhere.
Conversion Table: Fortnight to Sidereal Day
| Fortnight (fn) | Sidereal Day (sidereal day) |
|---|---|
| 1 | 14.038 |
| 5 | 70.192 |
| 10 | 140.383 |
| 25 | 350.958 |
| 50 | 701.917 |
| 100 | 1,403.833 |
| 500 | 7,019.165 |
| 1,000 | 14,038.331 |