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Time Converter

Convert time between milliseconds, seconds, minutes, hours, days, weeks, months and years, with a days-hours-minutes breakdown of any duration.

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Formula:

≈ means the result was rounded to the chosen number of significant figures.

“year” is the Julian year of exactly 365.25 days (the average including leap years, used in astronomy); “common year” is 365 days; a month is 1/12 of a Julian year (30.4375 days).

{value} in every unit

UnitResult

Quick conversion table: {from} to {to}

FromTo

Common values

ReferenceValueResult

Unit definitions

Unit

How to use the time converter

  1. Type a duration in Value. Decimals are fine (1.5 hours) and scientific notation works too (1e9 seconds).
  2. Choose the starting unit in From and the target unit in To, for example hour and minute.
  3. The result appears as you type, followed by the full line (“1.5 h = 90 min”). Copy puts that line on your clipboard.
  4. Breakdown: splits the same duration into days, hours, minutes and seconds, for example 100,000 s = 1 d 3 h 46 min 40 s.
  5. The Swap units button (⇄) reverses the conversion, and Significant figures controls the rounding (“≈” marks a rounded value).

Further down you will find the duration in every unit, a quick table for the chosen pair, a few landmarks (a day, a working week, a million and a billion seconds) and the length of each unit in seconds.

Units and definitions

Clock units are exact multiples of the SI second:

  • 1 minute = 60 s, 1 hour = 60 min = 3,600 s;
  • 1 day = 24 h = 86,400 s, 1 week = 7 days = 604,800 s;
  • 1 millisecond = 0.001 s.

Months and years are different, because calendar months have 28 to 31 days and years have 365 or 366 days. To stay consistent, this tool uses fixed conventions and says so in the unit names:

  • year (Julian, 365.25 days) = 31,557,600 s. This is the average year of the Julian calendar (three years of 365 days, then a leap year of 366) and the standard “year” of astronomy, used for light-years.
  • common year (365 days) = 31,536,000 s, the length of an ordinary calendar year.
  • month (average, 1/12 year) = 30.4375 days = 2,629,800 s.

The Gregorian calendar we use today averages 365.2425 days, because it skips three leap years every four centuries. The gap with the Julian year is about 11 minutes per year, which only matters over centuries. For exact calendar differences between two dates, a date calculator is the better tool.

Useful equivalences

  • 1 day = 1,440 minutes = 86,400 seconds.
  • 1 week = 168 hours = 10,080 minutes.
  • 1 Julian year = 8,766 hours = 525,960 minutes; a 365-day year has 525,600 minutes.
  • 1 million seconds ≈ 11.57 days; 1 billion seconds ≈ 31.7 years.
  • A 35-hour week is 2,100 minutes; a 40-hour week is 2,400 minutes.

Frequently asked questions

How many seconds are in a year?

31,536,000 seconds in a common year of 365 days, 31,622,400 in a leap year, and 31,557,600 in the Julian year of 365.25 days that this tool uses by default. Choose common year (365 days) if you want the calendar value.

How do I convert decimal hours to hours and minutes?

Enter the hours in Value with hour in From: the Breakdown: line gives the result directly. For example, 7.75 h is 7 h 45 min, because 0.75 × 60 = 45.

How long is a month in days?

On average 30.4375 days here (one twelfth of 365.25 days). Real months vary from 28 to 31 days, so convert months only when an average is what you need.

Why use 365.25 days for a year?

Because it includes leap years on average, which gives better results over several years than 365 days. It is also the definition used in astronomy. Both options are offered.

How long is a billion seconds?

About 31.7 years, or 11,574 days. A million seconds is only 11 days, 13 hours and 46 minutes.

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