Time Unit Converter
Convert nanoseconds to millennia: seconds, minutes, hours, days, weeks, months and years, with a duration breakdown.
Tool guide
What this tool does
Time Unit Converter changes durations between SI fractions of a second and calendar units up to millennia. It explains which month and year lengths it uses, and breaks any duration into days, hours, minutes and seconds.
Durations show up in every field: milliseconds in software logs, hours on timesheets, days in project plans and years in interest calculations. The small units are exact, but months and years are not, because calendar months range from 28 to 31 days and leap years add a day. A converter that hides its assumptions can give answers that look precise but are not.
Here the second is the base unit and everything up to the week is exact: a minute is 60 s, an hour 3,600 s, a day 86,400 s and a week 604,800 s. For longer periods the tool uses the average Gregorian year of 365.2425 days and an average month of one twelfth of that (30.436875 days), with a separate 365-day common year for contexts that require it. The breakdown panel turns large numbers like 1,000,000 seconds into readable days, hours and minutes. All work is done in your browser.
How to use Time Unit Converter
- Type a duration in the Value field.
- Select the unit you have in From and the one you need in To.
- Read and copy the Result, or swap the direction.
- Raise Decimal places for fractional results such as hours expressed in days.
- Use the breakdown panel to express an amount as days, hours, minutes and seconds.
- Paste a list of durations into Batch convert to convert them together.
Tips for better results
- One million seconds is about 11.6 days; one billion seconds is about 31.7 years.
- For payroll, converting minutes to decimal hours is easier with the Time to Decimal Hours Converter.
- Software timeouts are often in milliseconds: 30,000 ms is 30 seconds.
Common use cases
- Converting log timings and benchmark results between ns, µs, ms and s.
- Turning project estimates in hours into working days or weeks.
- Expressing an age or a long interval in days, weeks or seconds.
- Checking cache lifetimes and cookie expiry values given in seconds.
Common mistakes to avoid
- Assuming every month has 30 days; the average is closer to 30.44.
- Using 365 days per year for long periods, which drifts by about a day every four years.
- Confusing a working day of 8 hours with a calendar day of 24 hours.
Frequently asked questions
How many seconds are in a day?
A standard day is 86,400 seconds (24 × 60 × 60). Leap seconds occasionally added to UTC are ignored, as in most software.
How long is a month in this converter?
An average Gregorian month of 30.436875 days, which is one twelfth of 365.2425 days. Real months are 28 to 31 days, so use a date calculator for specific calendar dates.
How many hours are in a year?
An average Gregorian year has 8,765.82 hours; a common 365-day year has 8,760 hours and a leap year 8,784.
What is the difference between ms and µs?
A millisecond (ms) is a thousandth of a second; a microsecond (µs) is a millionth. So 1 ms equals 1,000 µs.
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