Fortnight to Sidereal Year Conversion Calculator: Free Online Tool

Convert fortnights to sidereal years with our free online time converter.

From:

Fortnight

To:

Sidereal Year

How to Use the Calculator:

Enter the value you want to convert in the 'From' field (Fortnight).
The converted value in Sidereal Year 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 Year

Converting Fortnight to Sidereal Year involves multiplying the value by a specific conversion factor, as shown in the formula below.

Formula:

1 Fortnight = 0.0383292 sidereal years

Example Calculation:

Convert 60 fortnights: 60 × 0.0383292 = 2.299755 sidereal years

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 Year?

A fortnight is a unit of time equal to exactly two weeks, which corresponds to 14 days or 336 hours.

A sidereal year is the time it takes for the Earth to complete one full orbit around the Sun relative to the distant, fixed stars. It represents the true orbital period of the Earth. Its duration is approximately 365.256363 mean solar days (or 365 days, 6 hours, 9 minutes, 9.76 seconds).

Note: The Fortnight is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Sidereal Year belongs to the imperial/US customary system.

History of the Fortnight and Sidereal Year

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 year emerged from ancient astronomers observing the Sun's apparent path against the background constellations (the ecliptic). They noticed that the Sun returned to the same position relative to specific stars after a consistent period. This stellar-based measurement was distinct from the tropical year (based on the seasons or equinoxes), which was more relevant for agriculture and calendars. Accurately determining the sidereal year was crucial for understanding the Earth's true orbital motion and for long-term astronomical predictions.

Common Uses for fortnights and sidereal years

Explore the typical applications for both Fortnight (imperial/US) and Sidereal Year (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 years

The sidereal year is primarily used in:

Astronomy & Astrophysics: For calculations involving the long-term orbital mechanics of the Earth and other celestial bodies within the solar system. It's fundamental for understanding the actual time it takes for planets to orbit the Sun.
Celestial Mechanics: Used in models predicting the positions of stars and planets over extended periods.
Defining Orbital Periods: Serves as the standard measure for the orbital period of Earth and is used comparatively for other planets.

It is generally not used for civil calendars, which are based on the tropical year to keep alignment with the seasons.

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 Year (sidereal year)

How long is a sidereal year in days?

A sidereal year is approximately 365.256363 mean solar days, which translates to about 365 days, 6 hours, 9 minutes, and 9.76 seconds.

What is the difference between a sidereal year and a tropical year?

A sidereal year measures the Earth's orbit relative to distant stars (one complete 360° revolution). A tropical year measures the time between successive vernal equinoxes (the start of spring in the Northern Hemisphere). Due to the precession of the equinoxes (a slow wobble in Earth's axis), the tropical year is slightly shorter (about 20 minutes) than the sidereal year (approx. 365.24219 days).

Why do calendars use the tropical year instead of the sidereal year?

Civil calendars, like the Gregorian calendar, are designed to keep the seasons occurring at roughly the same time each year. Since seasons are determined by the Earth's tilt and its position relative to the Sun (marked by equinoxes and solstices), the tropical year is the relevant measure for aligning the calendar with seasonal changes. Using the sidereal year would cause the seasons to gradually drift through the calendar months over centuries.

Conversion Table: Fortnight to Sidereal Year

Fortnight (fn)	Sidereal Year (sidereal year)
1	0.038
5	0.192
10	0.383
25	0.958
50	1.917
100	3.833
500	19.165
1,000	38.329

All Time Conversions

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