Understanding time
Seconds, minutes, and the long climb to a year.
One ladder, six rungs, and almost no two steps the same.
The ladder from second to day.
Time conversions look messy because the multipliers are inherited from astronomy — sixty seconds in a minute and sixty minutes in an hour come from the Babylonian sexagesimal system; twenty-four hours in a day comes from dividing daylight and darkness into twelve each. None of it is metric. All of it is unforgettable.
1 min = 60 s · 1 h = 3600 s · 1 d = 86 400 s
Weeks, months, years.
Above the day, the calendar takes over. A week is exactly seven days; a month is whatever the calendar says it is, which is why the converter uses thirty days as a working approximation; a year, similarly, runs about 365.25 days on average — give or take a leap day. For finance and contract work, always check which definition of month or year is being used.
Working approximations
- 1 week ≡ 7 days exactly
- 1 month ≈ 30 days (working average)
- 1 year ≈ 365 days (≈ 365.2425 with leap years)
- 1 year ≈ 31 557 600 s
Three worked conversions.
2 hours to seconds
1 h = 3600 s
An hour is bigger than a second, so the count grows — multiply.
2 × 3600 = 7200
= 7200 s
90 days to weeks
1 week = 7 days
A week is bigger than a day, so the count shrinks — divide.
90 ÷ 7 ≈ 12.857
= 12.857 weeks
500 milliseconds to seconds
1 s = 1000 ms
Milliseconds are smaller than seconds — divide by 1000.
500 ÷ 1000 = 0.5
= 0.5 s
A note on the SI second.
Since 1967, the second has been defined not by the Earth's rotation but by atomic physics — exactly 9 192 631 770 cycles of the radiation emitted by a specific transition in caesium-133. Every other time unit on this page is, ultimately, a multiple of that count. The Earth, it turned out, was less reliable than atoms.
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