How many seconds are in a day?

86,400 — 60 × 60 × 24. It is exact for a civil day, though the occasional leap second means a rare day is 86,401 seconds long in UTC.

How many days are in a year exactly?

365.2425 in the Gregorian calendar, which is why there is a leap year every four years except centuries not divisible by 400. That correction keeps the calendar aligned with the seasons to within a day over 3,000 years.

How many weeks are in a month?

About 4.35, not 4. The rounding is why twelve months of four weeks gives 48 weeks rather than 52, and why monthly and weekly budgets never quite reconcile.

Why isn't a month a fixed number of days?

Because the calendar descends from lunar months of about 29.5 days fitted awkwardly into a solar year. The result is months of 28 to 31 days, which is why any monthly calculation needs an averaging convention.

How many hours are in a work year?

About 2,080 for a 40-hour week over 52 weeks, before holidays. Subtracting typical leave and public holidays brings it closer to 1,850 to 1,900.

Time Converter

Convert milliseconds, seconds, minutes, hours, days, weeks and years.

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About the Time Converter

Convert between seconds, minutes, hours, days, weeks, months and years in one place. Values update as you type, and the result is calculated by converting to a base unit and back — so the arithmetic is the same in both directions and round-tripping a number returns exactly what you started with.

Everything up to a week is exact: 60 seconds to a minute, 24 hours to a day, 7 days to a week. Beyond that the units stop being fixed. A month is 28, 29, 30 or 31 days, and a year is 365 days except when it is 366.

The conversions here use the average Gregorian year of 365.2425 days and a month of 30.436875 days, which is that year divided by twelve. That makes twelve months equal one year exactly, which arithmetic using 30 or 365 does not — a difference that compounds visibly over any multi-year calculation.

How it works

Type a value and choose the units to convert between.
The result updates as you type, with the same value shown in every other unit below.
Jump straight to a direct page for the common conversions listed at the bottom.

Frequently asked questions

How many seconds are in a day?: 86,400 — 60 × 60 × 24. It is exact for a civil day, though the occasional leap second means a rare day is 86,401 seconds long in UTC.
How many days are in a year exactly?: 365.2425 in the Gregorian calendar, which is why there is a leap year every four years except centuries not divisible by 400. That correction keeps the calendar aligned with the seasons to within a day over 3,000 years.
How many weeks are in a month?: About 4.35, not 4. The rounding is why twelve months of four weeks gives 48 weeks rather than 52, and why monthly and weekly budgets never quite reconcile.
Why isn't a month a fixed number of days?: Because the calendar descends from lunar months of about 29.5 days fitted awkwardly into a solar year. The result is months of 28 to 31 days, which is why any monthly calculation needs an averaging convention.
How many hours are in a work year?: About 2,080 for a 40-hour week over 52 weeks, before holidays. Subtracting typical leave and public holidays brings it closer to 1,850 to 1,900.

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