How this calculator works
Seconds, minutes, hours, days and weeks are fixed multiples: 60 seconds to a minute, 60 minutes to an hour, 24 hours to a day and 7 days to a week. Months and years are not fixed, because the calendar month varies and a year is either 365 or 366 days. This page therefore uses average values. A year is the Julian year of 365.25 days, or 31,557,600 seconds, and a month is one twelfth of that year, or 2,629,800 seconds, which is 30.4375 days. Those averages are convenient for durations but not for finding a calendar date.
Formula
seconds = value x F(unit). F is 1 for seconds, 60 for minutes, 3,600 for hours, 86,400 for days, 604,800 for weeks, 2,629,800 for average months and 31,557,600 for Julian years. Divide by the same factor to convert back.
Worked example
1 day is 24 hours, 1,440 minutes, 86,400 seconds and 0.142857 weeks. 1 year is 365.25 days, 52.1786 weeks and 12 average months. 90 minutes is 1.5 hours and 5,400 seconds.
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Frequently asked questions
Why is a month 30.4375 days here?
Twelve average months must fit into one Julian year of 365.25 days, so each month is 365.25 / 12 = 30.4375 days. Calendar months have 28 to 31 days, so a result in months is an average, not a date.
Should I use this page for calendar dates?
No. For adding months or years to a date, a calendar calculator that knows which months are being crossed is the right tool. This page converts durations.
Are leap seconds included?
No. The page uses the fixed 86,400-second day of ordinary timekeeping and ignores leap seconds, which are rare steps inserted into UTC.