Time Unit Converter
Convert between nanoseconds, microseconds, milliseconds, seconds, minutes, hours, days, weeks, months, years, decades, and centuries. All conversions update instantly.
| Unit | Value |
|---|---|
| Nanosecond (ns) | 3600000000000 |
| Microsecond (µs) | 3600000000 |
| Millisecond (ms) | 3600000 |
| Second (s) | 3600 |
| Minute (min) | 60 |
| Hour (h) | 1 |
| Day (d) | 0.041667 |
| Week (wk) | 0.005952 |
| Month (avg) | 0.001369 |
| Year (yr) | 0.000114 |
| Decade | 0.000011 |
| Century | 0.000001 |
SI Time Units
The second (s) is the SI base unit of time, defined since 1967 by the cesium atomic clock: exactly 9,192,631,770 oscillations of the radiation emitted by a cesium-133 atom transitioning between two hyperfine energy levels. This definition is so precise that the best atomic clocks will not gain or lose a second in roughly 300 million years.
Above the second, SI uses the same "multiply by 60" pattern that originated in ancient Babylon: 60 seconds in a minute, 60 minutes in an hour. Above hours, the day (24 hours), week, month, and year are not SI units but are accepted for use with SI. Below the second, SI uses standard metric prefixes:
| Unit | Symbol | Seconds | Common use |
|---|---|---|---|
| Nanosecond | ns | 10⁻⁹ (0.000000001) | Processor clock cycles, light travel distance (30 cm/ns) |
| Microsecond | µs | 10⁻⁶ (0.000001) | Radio frequency periods, flash memory read latency |
| Millisecond | ms | 10⁻³ (0.001) | Network ping, animation frames, audio latency |
| Second | s | 1 | SI base unit; heartbeat, camera shutter |
| Minute | min | 60 | Cooking, workout timing, meeting scheduling |
| Hour | h | 3,600 | Work hours, travel time, billing periods |
| Day | d | 86,400 | Calendar, sleep cycles, Unix timestamp unit |
Nanoseconds and Computing
The nanosecond — one billionth of a second — became a practically important unit with the rise of modern computing. A 3 GHz processor completes about 3 billion clock cycles per second, which means each cycle takes approximately 0.33 nanoseconds. During one nanosecond, light in a vacuum travels about 30 centimeters (roughly one foot). This is why data center architects care deeply about the physical distance between servers: a server 30 meters away introduces a minimum 100 ns round-trip latency, even at the speed of light.
DRAM memory has a typical access latency of 60–100 nanoseconds, while CPU caches operate in 1–10 nanoseconds. NVMe solid-state drives reach about 100 microseconds (100,000 ns), and traditional spinning hard drives around 10 milliseconds (10,000,000 ns). Understanding these orders of magnitude is essential for writing high-performance software.
The History of Time Measurement
The division of the day into 24 hours, 60 minutes, and 60 seconds traces back to ancient Mesopotamia. Babylonian astronomers used a base-60 (sexagesimal) number system around 2000 BCE. They divided the night into 12 parts (based on rising star groups called decans), and matched the day into 12 parts, yielding 24 total. The division of hours into 60 minutes and minutes into 60 seconds follows the same sexagesimal logic. Egyptian water clocks (clepsydrae) and sundials operationalised these divisions in everyday life.
Mechanical clocks with minute hands appeared in Europe in the late 16th century. Accurate seconds pendulums were developed in the 17th century by Christiaan Huygens. The second as a formal unit — 1/86,400 of a mean solar day — was standardised in the 19th century. It was not until 1967 that the second was redefined in terms of atomic physics, divorcing timekeeping from the slightly irregular rotation of the Earth.
Leap Years and Calendar Complexity
The mismatch between the solar year (365.2422 days) and a whole number of days drives all calendar complexity. The Julian calendar (introduced by Julius Caesar in 46 BCE) added a leap day every 4 years, giving 365.25 days/year — an overestimate of about 11 minutes per year. By 1582, this had accumulated a 10-day error. Pope Gregory XIII introduced the Gregorian reform: skip the leap day in century years (1700, 1800, 1900) unless divisible by 400 (2000). This gives 365.2425 days/year — accurate to within about 26 seconds per year.
Beyond the year, days themselves are not perfectly uniform. Tidal friction is slowly lengthening Earth's rotation. The International Earth Rotation and Reference Systems Service (IERS) occasionally inserts "leap seconds" into UTC to keep civil time aligned with astronomical time. Since 1972, 27 leap seconds have been added. In 2035, a new time standard (UTC-SLS or similar) will likely be adopted to phase out leap seconds, as they cause problems for computer networks and financial systems.
Why Months Are Unequal
The calendar months have 28, 29, 30, or 31 days — a historical accident compounded over millennia. The Roman calendar originally had 10 months (304 days), with the remaining winter days unaccounted for. King Numa Pompilius added January and February around 713 BCE to fill the gap. Julius Caesar's reform in 46 BCE established the 12-month year of 365 days, and August was later extended to 31 days to match July (named for Julius Caesar) when Emperor Augustus lent his name to the eighth month. February was shortened to compensate.
The practical consequence for conversion is that "one month" is not a fixed number of days. For this reason, this converter uses the average month length of 365.25 ÷ 12 = 30.4375 days (2,629,800 seconds). If you need an exact day count for a specific month, use the Date Calculator instead.
Average Month: 30.44 Days Explained
The "average month" used in this converter is 365.25 ÷ 12 = 30.4375 days, or 2,629,800 seconds. This is derived from the Julian year (365.25 days), which is itself an average accounting for the leap year cycle. The distribution across months is: 7 months have 31 days, 4 months have 30 days, and February has 28 (or 29 in a leap year). The mean of [31,31,31,31,31,31,31,30,30,30,30,28] = 365/12 ≈ 30.4167 days for a common year, or 366/12 = 30.5 for a leap year, averaging to about 30.44 days per month over the 4-year Gregorian cycle.
Quick Reference: Key Time Conversions
| From | To | Multiply by | Value |
|---|---|---|---|
| 1 minute | seconds | 60 | 60 s |
| 1 hour | seconds | 3,600 | 3,600 s |
| 1 hour | minutes | 60 | 60 min |
| 1 day | hours | 24 | 24 h |
| 1 day | seconds | 86,400 | 86,400 s |
| 1 week | days | 7 | 7 d |
| 1 week | hours | 168 | 168 h |
| 1 month (avg) | days | 30.4375 | 30.44 d |
| 1 year | days | 365.25 | 365.25 d |
| 1 year | hours | 8,766 | 8,766 h |
| 1 year | seconds | 31,557,600 | 31,557,600 s |
| 1 decade | years | 10 | 10 yr |
| 1 century | years | 100 | 100 yr |
Frequently Asked Questions
How many seconds are in a day?
There are exactly 86,400 seconds in a standard (non-leap) day. The calculation is straightforward: 1 day = 24 hours, 1 hour = 60 minutes, 1 minute = 60 seconds. So 24 × 60 × 60 = 86,400. This figure is fundamental in computing — Unix timestamps count seconds since the Unix epoch (January 1, 1970), and many networking and scheduling systems work in seconds. Note that on days when a leap second is inserted (a rare event managed by the International Earth Rotation and Reference Systems Service), a day may have 86,401 seconds. There have been 27 leap seconds added since 1972.
How many days are in a year?
A common calendar year has 365 days. A leap year has 366. The precise astronomical figure — the mean tropical year, which measures the time from one spring equinox to the next — is approximately 365.2422 days. The Gregorian calendar approximates this with a rule: add a leap day every 4 years, except for century years (1900, 2100), except again for years divisible by 400 (2000, 2400). This gives an average of 365.2425 days per year — close enough that the Gregorian calendar drifts only about 1 day in 3,030 years relative to the tropical year. This converter uses 365.25 days/year (31,557,600 seconds), which is the Julian year used in astronomy.
How many weeks are in a month?
A calendar month contains roughly 4.348 weeks on average, because the average month is 30.4375 days (365.25 ÷ 12) and a week is 7 days: 30.4375 ÷ 7 ≈ 4.348. This is why "a month is about 4 weeks" is a useful approximation for scheduling, but it underestimates by about 2 days per month — which adds up to about 24 days over a year. In practice: 6 months is not 24 weeks but rather about 26 weeks (half a year = 182.6 days ÷ 7 ≈ 26.1 weeks). This converter uses an average month of 365.25 ÷ 12 = 30.4375 days = 2,629,800 seconds.
How many milliseconds are in a second?
There are exactly 1,000 milliseconds in one second. The prefix "milli" means one-thousandth (10⁻³). So 1 ms = 0.001 s, and 1 s = 1,000 ms. Milliseconds are the standard precision unit for many computing operations: HTTP request latency, database query time, animation frame timing (a 60 fps animation renders a frame every 16.67 ms), audio latency, and network round-trip time. A good broadband connection has a ping (round-trip time) of 10–30 ms. Human reaction time is typically 150–300 ms. A hummingbird flaps its wings once every 4–5 ms.
What is the difference between a solar year and a calendar year?
A solar (or tropical) year is the time Earth takes to complete one orbit around the Sun relative to the vernal equinox: approximately 365 days, 5 hours, 48 minutes, and 45 seconds (365.2422 days). A calendar year is a fixed administrative unit: 365 days in a common year, 366 in a leap year. The Gregorian calendar's averaging rule (365.2425 days/year) keeps these aligned to within 1 day per ~3,000 years. The Julian year used in astronomy is exactly 365.25 days (31,557,600 seconds) — simpler but slightly longer than the tropical year. The sidereal year (Earth's orbit relative to distant stars) is 365.2564 days, slightly longer than the tropical year because of the precession of Earth's axis.
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