A fortnight is exactly two weeks, which equals 14 days, 336 hours, or 1,209,600 seconds. The word comes from Old English meaning fourteen nights. It is still commonly used in UK and Australian English, especially for payroll, benefits, rental periods, and everyday speech.

Time Converter

Q: How many seconds are in an hour?

1 hour = 60 minutes × 60 seconds = 3,600 seconds. Additional conversions: 1 hour = 3,600 seconds = 3,600,000 milliseconds = 3,600,000,000 microseconds. 24 hours, or 1 day, = 86,400 seconds. 1 week = 604,800 seconds. 1 calendar year = 31,536,000 seconds in a common year or 31,622,400 seconds in a leap year.

Q: How do I convert minutes to decimal hours for a timesheet?

Divide the number of minutes by 60. For example, 30 minutes = 0.5 hours, 45 minutes = 0.75 hours, 90 minutes = 1.5 hours, 105 minutes = 1.75 hours, and 135 minutes = 2.25 hours. If you need to convert hours and minutes together, convert the minutes to a decimal and add them to the whole hours. For example, 2 hours 35 minutes becomes 2 + (35 ÷ 60) = 2.5833 hours, often rounded to 2.58.

Q: What is a sidereal day and how does it differ from a solar day?

A sidereal day is the time Earth takes to complete one full rotation relative to distant stars: 23 hours 56 minutes 4.091 seconds, or about 86,164.1 seconds. A mean solar day is 24 hours, or 86,400 seconds. The sidereal day is about 3 minutes 55.91 seconds shorter. The difference exists because Earth is also orbiting the Sun, so it must rotate slightly more than 360 degrees for the Sun to appear in the same place in the sky again. Astronomers use sidereal time, while everyday timekeeping uses solar time.

Q: What is a shake and where is it used?

A shake is a unit of time equal to 10 nanoseconds, or 1 × 10^-8 seconds. It is used informally in nuclear physics and weapons research for timing very rapid processes such as fission chain reactions. The name comes from the phrase 'two shakes of a lamb's tail,' meaning a very short time. Even though the name sounds informal, it appears in technical contexts where events occur on the scale of tens of nanoseconds.

Q: What is the difference between the tropical year and the sidereal year?

The tropical year, about 365.24219 days, is the time between successive vernal equinoxes and is the basis of the calendar year. The sidereal year, about 365.25636 days, is the time Earth takes to complete one orbit relative to distant stars. The tropical year is about 20 minutes shorter. This difference is caused by the slow precession of Earth's axis, which makes the equinoxes drift gradually relative to the stars. For calendar and civil use, the tropical year is the relevant one.

Convert time units instantly—milliseconds, seconds, minutes, hours, days, and more. Enter a value, choose units, and get accurate results in seconds. Perfect for work logs, study tracking, project planning, coding, and technical documentation. Free and easy to use.

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Time Converter

The Time Converter converts between 23 time duration units spanning sub-second scientific units (femtosecond through millisecond), everyday civil time (second through century), and astronomical sidereal time (sidereal second through sidereal year), plus three distinct year definitions and historical units including the fortnight and shake. Select the From and To units, enter the value, and click Convert.

This is a duration converter — it converts lengths of time between units. It does not convert between time zones or between points on the clock. Common uses include timesheet calculations (minutes to decimal hours), software development (milliseconds to seconds for timeouts and frame rates), project planning (days to weeks), scientific work (nanoseconds to seconds for frequency calculations), and astronomy (sidereal to mean solar time).

How to use the Time Converter

Enter the time duration value to convert.
Select the From unit — the unit your value is currently in.
Select the To unit — the unit you want to convert to.
Click Convert. The result is displayed immediately.
To convert the same value to additional units, change the To dropdown and click Convert again.

All 23 units — values in seconds and typical contexts

The table below covers all 23 supported units organized by category, with their value in seconds and the context in which each is typically used:

Unit	In seconds	Typical context
Sub-second scientific units
Femtosecond (fs)	1e-15 s	Laser pulse durations, ultrafast spectroscopy, chemical reaction timescales. The fastest events in chemistry and photonics are measured in femtoseconds. A femtosecond is to one second what one second is to approximately 31.7 million years.
Picosecond (ps)	1e-12 s	Semiconductor switching times, THz spectroscopy, some chemical bond vibrations. High-speed electronics and some radar systems operate at picosecond timescales. Light travels approximately 0.3 mm in one picosecond.
Nanosecond (ns)	1e-9 s	CPU clock cycles (a 3 GHz processor executes one cycle every ~0.33 ns), RAM latency, network packet transmission, GPS signal processing. Light travels approximately 30 cm in one nanosecond.
Shake	1e-8 s (10 ns)	Nuclear physics and weapons research: 1 shake = 10 nanoseconds. The name comes from the phrase 'two shakes of a lamb's tail' — a colloquial way of saying 'a very short time'. Used informally in fission chain reaction timing calculations.
Microsecond (us)	1e-6 s	Software performance benchmarking, database query latency, OS scheduling intervals, radio frequency cycles. A typical SSD access time is 50–100 microseconds. 1 microsecond = 1,000 nanoseconds.
Millisecond (ms)	0.001 s	Application timeouts, animation frame intervals (60 fps = 16.67 ms per frame), ping/latency measurements, human reaction times (~150–300 ms), audio processing, keypress debounce in electronics.
Everyday civil time units (mean solar)
Second (mean solar)	1 s	The SI base unit of time. Defined since 1967 by atomic physics: exactly 9,192,631,770 oscillations of the caesium-133 atom. All modern timekeeping is based on atomic seconds.
Minute (mean solar)	60 s	Short durations in everyday scheduling, cooking, exercise, meeting durations, and time tracking.
Hour (mean solar)	3,600 s	Work hours, travel times, billing periods, shift durations, flight times. 1 hour = 60 minutes = 3,600 seconds.
Day (mean solar)	86,400 s	The mean solar day is the average time for the Sun to return to the same position in the sky. 1 day = 24 hours = 1,440 minutes = 86,400 seconds. The standard calendar day.
Week	604,800 s	Project planning, scheduling, payroll, work cycles. 1 week = 7 days = 168 hours = 604,800 seconds.
Fortnight	1,209,600 s	Exactly 2 weeks = 14 days. Still used in UK payroll (fortnightly pay), Australian/UK legislation, some rental agreements, and everyday speech in some English-speaking countries.
Month (mean calendar)	2,629,800 s (avg)	The mean calendar month is approximately 30.4375 days (365.25 days / 12). Calendar months vary from 28 to 31 days. Used for billing cycles, subscription periods, project timelines, and payroll.
Quarter	7,889,400 s (avg)	Exactly 3 months = approximately 91.3 days. Used in finance (quarterly earnings, quarterly payments), business planning, and fiscal year reporting.
Year (calendar)	31,536,000 s	The Gregorian calendar year: 365 days (366 in leap years). 365 days = 31,536,000 seconds; 366 days = 31,622,400 seconds. Used for all standard civil and legal date calculations.
Decade	315,360,000 s	Historical periodization, long-term trends, generational analysis, compound interest calculations over long periods. 1 decade = 10 calendar years.
Century	3,153,600,000 s	Historical and geological time, radiocarbon dating context, long-term actuarial calculations. 1 century = 100 years = 36,524.25 days (including leap years).
Sidereal units (astronomy)
Second (sidereal)	0.99727 s	1/86,400 of a sidereal day. Used in astronomical calculations and telescope tracking systems.
Minute (sidereal)	59.836 s	60 sidereal seconds. Used in astronomical coordinate and timing calculations.
Hour (sidereal)	3,590.17 s	60 sidereal minutes. Right ascension in astronomy is measured in sidereal hours.
Day (sidereal)	86,164.1 s	The time for Earth to complete one full rotation relative to distant stars: approximately 23 hours 56 minutes 4.091 seconds. Approximately 3 minutes 55.91 seconds shorter than the mean solar day. Used to set telescope tracking rates and compute star positions.
Year (sidereal)	31,558,149.8 s	The time for Earth to complete one full orbit around the Sun relative to distant stars: approximately 365.256363 days. Slightly longer than the tropical year due to precession. Used in astronomy for orbital period calculations.
Year (tropical)	31,556,925.2 s	The time between successive vernal (spring) equinoxes: approximately 365.242190 days. This is the year length on which the Gregorian calendar is based — the calendar is designed to keep the equinox on approximately the same date each year.

Sidereal vs mean solar time — what the difference means

Several units in the converter come in two versions: mean solar and sidereal. The distinction matters for astronomy and telescope operation but is often confusing for general users.

Mean solar time

Mean solar time is based on the average position of the Sun in the sky. The mean solar day (24 hours = 86,400 seconds) is the average time it takes for the Sun to return to the same position relative to Earth. This is what clocks and calendars use — it is the everyday second, minute, hour, and day.

Sidereal time

Sidereal time is based on Earth's rotation relative to distant stars (rather than the Sun). Because Earth is simultaneously rotating and orbiting the Sun, these two reference frames produce slightly different day lengths. The sidereal day (23 hours 56 minutes 4.091 seconds = 86,164.1 s) is approximately 3 minutes 55.91 seconds shorter than the mean solar day. Over a full year, this produces exactly one extra sidereal day compared to mean solar days — Earth makes 366.25 sidereal rotations per year but only 365.25 solar days.

Telescopes and observatories use sidereal time because stars move across the sky at the sidereal rate — they return to the same position in the sky every sidereal day (23h 56m 4s), not every solar day (24h). Right ascension (one of the two coordinates for locating objects in the sky) is measured in sidereal hours. If you are configuring telescope tracking software, mount alignment, or working with right ascension coordinates, use sidereal time. For all other purposes — scheduling, timesheets, project planning, software development — use mean solar units.

Three year definitions — calendar, sidereal, and tropical

Calendar year (Gregorian)

The calendar year is defined as 365 days (366 in leap years) = 31,536,000 seconds (31,622,400 in a leap year). The Gregorian calendar averages 365.2425 days per year by adding a leap day every 4 years, skipping it every 100 years, and reinstating it every 400 years. Used for all civil, legal, and business date calculations.

Tropical year

The tropical year is the time between successive vernal equinoxes (the moment the Sun crosses the celestial equator heading northward, marking the astronomical start of spring in the Northern Hemisphere). Its length is approximately 365.242190 days = 31,556,925.2 seconds. The Gregorian calendar is designed to approximate the tropical year — keeping the equinox on approximately the same calendar date each year.

Sidereal year

The sidereal year is the time for Earth to complete one full orbit around the Sun relative to distant stars: approximately 365.256363 days = 31,558,149.8 seconds. It is slightly longer than the tropical year (by about 20 minutes) due to the precession of Earth's axis — a slow wobble that causes the equinoxes to drift relative to the stars over a ~26,000-year cycle.

The difference between the three year types is small in absolute terms (the tropical year is approximately 20 minutes shorter than the sidereal year) but accumulates significantly over long periods. If you are calculating dates using years (e.g. converting '5 years in seconds' for a software timestamp or legal period), the calendar year (31,536,000 seconds for a common year, 31,622,400 for a leap year) is the correct choice for all civil and business purposes.

Common use cases

Context	Common conversion	Notes
Timesheets and work tracking	minutes to hours	Convert total minutes worked to hours for billing and payroll. 90 minutes = 1.5 hours; 105 minutes = 1.75 hours; 150 minutes = 2.5 hours. Many time-tracking apps log in minutes; billing is in decimal hours.
Software development — timeouts and delays	ms to seconds, seconds to ms	API timeouts, database query limits, animation durations, and debounce intervals are commonly set in milliseconds in code. A 30-second API timeout = 30,000 ms. A 60 fps animation frame = 16.67 ms. HTTP timeout headers are in seconds; JavaScript setTimeout is in milliseconds.
Project planning and scheduling	days to weeks, weeks to months	Convert sprint durations, milestone timelines, and project phases between days, weeks, and months. A 90-day project = approximately 12.9 weeks = approximately 3 months. Note that 3 months is not always exactly 90 days due to varying month lengths.
Scientific and engineering calculations	ns to ms, us to seconds	Physics, electronics, and chemistry calculations often require consistent time units. Convert nanoseconds to seconds for frequency calculations (1 GHz = 1 cycle per nanosecond = 10^9 Hz). Convert microseconds to milliseconds for latency comparisons.
Historical and geological time	years to decades to centuries	Express historical periods in convenient units. The industrial revolution began approximately 250 years ago = 25 decades = 2.5 centuries. Earth's age is approximately 4.54 billion years = 45.4 million decades.
Astronomy and telescope operation	sidereal to mean solar	Telescopes track stars using sidereal time (based on Earth's rotation relative to stars). 1 sidereal day = 23h 56m 4.091s mean solar time. Right ascension is measured in sidereal hours. Satellite orbit periods are calculated in sidereal time.

Usage limits

Account type	Daily conversions
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Registered	100 per day

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Frequently asked questions

How many seconds are in an hour?

1 hour = 60 minutes x 60 seconds = 3,600 seconds. Additional conversions: 1 hour = 3,600 seconds = 3,600,000 milliseconds = 3,600,000,000 microseconds. 24 hours (1 day) = 86,400 seconds. 1 week = 604,800 seconds. 1 year (calendar) = 31,536,000 seconds (common year) or 31,622,400 seconds (leap year).

How do I convert minutes to decimal hours for a timesheet?

Divide the minutes by 60. Examples: 30 minutes = 30/60 = 0.5 hours; 45 minutes = 0.75 hours; 90 minutes = 1.5 hours; 105 minutes = 1.75 hours; 135 minutes = 2.25 hours. For timesheet billing, enter the decimal hours value directly. If you need to convert hours and minutes (e.g. 2 hours 35 minutes): convert the minutes component to decimal (35/60 = 0.5833) and add to the hours (2 + 0.5833 = 2.5833 hours, commonly rounded to 2.58).

What is a sidereal day and how does it differ from a solar day?

A sidereal day is the time for Earth to complete one full rotation relative to distant stars: 23 hours 56 minutes 4.091 seconds = 86,164.1 seconds. A mean solar day is 24 hours = 86,400 seconds. The sidereal day is approximately 3 minutes 55.91 seconds shorter. The difference arises because Earth also orbits the Sun — as it moves along its orbit, it needs to rotate slightly more than 360 degrees for the Sun to return to the same position in the sky (solar day), but exactly 360 degrees for a distant star to return (sidereal day). Astronomers and telescope tracking systems use sidereal time; everyday timekeeping uses solar time.

What is a fortnight?

A fortnight is exactly two weeks = 14 days = 336 hours = 1,209,600 seconds. The word derives from Old English 'feowertyne niht' (fourteen nights). Fortnights are still commonly used in UK and Australian English for payroll periods (fortnightly pay), some legislation, and everyday speech. A fortnight in Australia corresponds to a two-week pay cycle; in the UK, many government benefits and rental agreements operate on a fortnightly cycle.

What is a shake and where is it used?

A shake is a unit of time equal to 10 nanoseconds (1e-8 seconds). It is used informally in nuclear physics and weapons research for timing fission chain reactions, where events occur on a 10-nanosecond scale. The name comes from the expression 'two shakes of a lamb's tail' — a colloquial phrase for 'a very short time'. Despite the informal-sounding name, the shake is a defined unit used in technical literature: a nuclear chain reaction typically runs its course in a few tens of shakes (tens to hundreds of nanoseconds).

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

The tropical year (365.24219 days) is the time between successive vernal equinoxes — the basis for the calendar. The sidereal year (365.25636 days) is the time for Earth to complete one full orbit relative to distant stars. The tropical year is approximately 20 minutes shorter than the sidereal year. The difference is caused by the precession of Earth's axis — a slow wobble with a period of approximately 26,000 years — which causes the equinoxes to drift slowly relative to the star background. For all calendar and civil purposes, use the calendar year definition.

How many milliseconds in a second, and why does it matter for developers?

1 second = 1,000 milliseconds = 1,000,000 microseconds = 1,000,000,000 nanoseconds. The millisecond matters for developers because many programming environments and APIs use milliseconds as their default time unit: JavaScript's setTimeout and setInterval take values in milliseconds; Unix timestamps are commonly in milliseconds; HTTP headers like Retry-After are in seconds; database query timeouts vary by platform. A common bug is passing a value in the wrong unit — setting a 30-second timeout as 30 ms (30,000x too short) or 30,000 seconds (500 minutes, 30,000x too long). Always check which unit a function expects before passing a time value.

Is the Time Converter free?

Yes. The converter is free within the daily usage limits shown above. Guest users can perform 25 conversions per day without creating an account. Registering a free ToolsPiNG account increases the daily limit to 100 conversions per day.