Time converter
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Other units
- Second (s) 1
- Millisecond (ms) 1000
- Minute (min) 0.016666667
- Hour (h) 0.000277778
- Day (d) 0.000011574
- Week (wk) 0.000001653
- Month (30 days) (mo) 3.858025×10⁻⁷
- Year (365 days) (yr) 3.170979×10⁻⁸
Reviewed on by the Skala Convert team
Time converts through the second. A minute is 60 s, an hour 3,600 s, a day 86,400 s and a week 604,800 s. On this site a month is 30 days and a year is 365 days.
How is a time conversion calculated?
Convert to seconds, then to the target unit. Ninety minutes to hours: 90 × 60 = 5,400 s, and 5,400 ÷ 3,600 = 1.5 h. Minutes and seconds come in sixties, a habit inherited from the base-60 arithmetic of ancient Mesopotamia, which Greek astronomers later applied to the hour; the division of the day into 24 hours goes back to ancient Egypt.
Why are month and year fixed at 30 and 365 days?
Because calendar months and years are not constant. Months run from 28 to 31 days, and the Gregorian calendar’s year averages 365.2425 days once leap years are counted. A converter needs a fixed number, so this one uses a 30-day month and a 365-day year, and labels them that way. If you need the calendar average instead, a mean month is 30.44 days. Astronomers use yet another year, the Julian year of exactly 365.25 days, which is the one inside the definition of a light-year.
What is the most common time mistake?
Reading decimal hours as minutes. 1.5 hours is 1 hour 30 minutes, not 1 hour 50 minutes, and 0.1 hours is 6 minutes. Timesheets and flight logs that record decimal hours catch people out constantly. To turn the decimal part into minutes, multiply it by 60.
What defines a second?
An atom. Since 1967 the second has been the duration of 9,192,631,770 cycles of the radiation from a specific transition in the caesium-133 atom — the principle behind atomic clocks. Before that it was a fraction of the day, which proved unreliable because the Earth’s rotation is slightly irregular. That irregularity is also why leap seconds exist; in 2022 the General Conference on Weights and Measures decided to effectively end them by 2035.
Frequently asked questions
How many seconds are in a day?
86,400: 24 hours × 60 minutes × 60 seconds.
How do I convert decimal hours to hours and minutes?
Keep the whole number as hours and multiply the decimal part by 60. 2.75 hours is 2 hours and 0.75 × 60 = 45 minutes.
How many hours are in a year?
8,760 in a 365-day year, and 8,784 in a leap year.
Why does this converter use a 30-day month?
Calendar months vary from 28 to 31 days, so a fixed value is needed for a conversion. The unit is labeled “Month (30 days)” to make that explicit.