Time units are a mix of decimal and non-decimal steps: 1,000 milliseconds in a second, but 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day and 7 days in a week. Months and years are worse, because they are tied to the Moon and the Sun rather than to the second. This converter handles 16 units, from nanoseconds to millennia, uses clearly stated averages for months and years, and breaks any result into days, hours, minutes and seconds.
How to use the time unit converter
- Enter a duration in Value.
- Choose its unit in From and the target unit in To.
- The tape shows the result, both factors and the duration written out in days, hours, minutes and seconds.
- The table lists the same duration in every unit, including the three kinds of year.
Time conversion formula
Every unit is defined as a number of seconds, the SI base unit:
Fixed relationships: 1 min = 60 s, 1 h = 3,600 s, 1 day = 86,400 s, 1 week = 604,800 s. For longer periods the converter uses:
- Year (Gregorian average): 365.2425 days = 31,556,952 s. This reflects the leap-year rule (every 4 years, except century years not divisible by 400).
- Common year: 365 days. Julian year: 365.25 days, the astronomer’s standard.
- Month: one twelfth of the Gregorian year, 30.436875 days.
- Decade, century, millennium: 10, 100 and 1,000 Gregorian years.
Worked example: two weeks of vacation
How many minutes are in a two-week vacation?
2 weeks × 10,080 min/week = 20,160 minutes
Check: 2 × 7 days × 24 h × 60 min = 20,160. In hours, that is 336.
A larger example: one billion seconds ÷ 31,556,952 s per year = 31.69 years, or about 11,574 days.
Common time conversions
| From | To | Multiply by |
|---|---|---|
| minutes | seconds | 60 |
| hours | minutes | 60 |
| hours | seconds | 3,600 |
| days | hours | 24 |
| days | seconds | 86,400 |
| weeks | hours | 168 |
| weeks | minutes | 10,080 |
| common years | hours | 8,760 |
| Gregorian years | days | 365.2425 |
| Gregorian years | seconds | 31,556,952 |
Which “year” should you use?
For ages, payroll and anniversaries, count actual calendar years with a date tool such as the date difference calculator, because leap days fall on specific dates. For averages over long spans, such as converting a lifetime or an interest period, the Gregorian 365.2425-day year is the most accurate. Scientific papers often state durations in Julian years, written “a” (annum), so a “megayear” (Ma) is a million Julian years. If you only need a quick 365-day year, select “common year.”
Precision notes
Leap seconds. Coordinated Universal Time has occasionally inserted a leap second to stay aligned with Earth’s rotation, but these are not included in unit conversions; a day here is always 86,400 SI seconds. International timekeeping bodies have agreed to stop adding leap seconds by 2035.
Months are averages. Converting “3 months” to days gives 91.31 days, not 90 or 92. For billing periods or due dates, use calendar math instead.
Decimal hours. Timesheets often record 7.75 hours rather than 7 hours 45 minutes. The hours to minutes and minutes to hours converters handle that format directly, and the hours to days converter can count 8-hour workdays.
To add or subtract clock times, use the time duration calculator.
Frequently asked questions
How many seconds are in a year?
It depends on the year. A 365-day common year has 31,536,000 seconds, a leap year 31,622,400, and the average Gregorian year of 365.2425 days has 31,556,952. Astronomers often use the Julian year of exactly 365.25 days, 31,557,600 seconds.
How long is a month in seconds or days?
Calendar months run from 28 to 31 days, so converters use an average. Over the 400-year Gregorian cycle, a month averages 30.436875 days, which is 2,629,746 seconds.
How many minutes are in a week?
10,080: 7 days × 24 hours × 60 minutes. Two weeks, a fortnight, contain 20,160 minutes.
How long is a billion seconds?
About 31.7 years (11,574 days). A million seconds, by comparison, is only about 11.6 days.