Time Unit Converter — Seconds, Minutes, Days, Years Free
Convert time between nanoseconds, milliseconds, seconds, minutes, hours, days, weeks, months, years, decades, centuries. Free.
About Time Unit Converter
A time-unit converter translates a duration between scales — from nanoseconds (computing) up to centuries (history). Useful for: software performance work (latency in ns / μs / ms), human-time conversions (How many minutes in a day? 1440), age calculation, project planning ("18 months = 1.5 years = 547 days"), and intuition for very large or small durations. The ZTools Time Unit Converter handles 12+ units, with explicit handling of "month" and "year" being non-fixed lengths (default to Gregorian average: month = 30.4375 days, year = 365.25 days; selectable to "common year" 365 days or "leap year" 366).
Use cases
- Performance / latency conversion. API responds in 245 ms; database query takes 12 µs. Convert to consistent unit (e.g. ms) for comparison and budgeting.
- Project / contract durations. Contract is 18 months; how many days for resource planning? 547. How many work days (excluding weekends)? ~390.
- Age / lifespan. Average human lifespan ~80 years ≈ 2.5 billion seconds. Quick conversion drives intuition for "how much time do I have".
- Astronomical durations. Earth orbits sun every 365.256 days = 31.558 million seconds. Useful for orbital mechanics and physics.
How it works
- Enter value + source unit. Numeric input; pick ns / µs / ms / s / min / hr / day / week / month / year / decade / century.
- View all conversions. Result in 12+ units simultaneously.
- Pick year length. 365 days (common year), 366 (leap), 365.25 (average), 365.2425 (Gregorian average — accounts for century rules).
- Pick month length. 28 / 29 / 30 / 31 / 30.4375 (average) / 30.4368 (Gregorian average).
Examples
Input: 1 day
Output: 24 hr, 1440 min, 86,400 s, 86.4 million ms.
Input: 1 year (Gregorian average)
Output: 365.2425 days, 8765.82 hr, 525,949 min, 31.557 million s.
Input: 1 minute
Output: 60 s, 60,000 ms, 60 million µs, 60 billion ns.
Input: Average human life (80 years)
Output: ~2.524 billion s, ~70,000 hr, ~29,200 days. Surprising at this resolution.
Frequently asked questions
Why are months and years not fixed?
Months range 28–31 days (Feb is 28, Apr is 30, etc.). Years are 365 except leap years (every 4, except century-not-divisible-by-400). Tool defaults to Gregorian average (365.2425 days/year) for accurate long-term math.
What's a "Julian year"?
365.25 days exactly — used in astronomy and many SI definitions. Slightly longer than Gregorian (365.2425). Difference matters over millennia.
Difference between ms / µs / ns?
1 ms = 1000 µs = 1,000,000 ns. Modern hardware operates at ns / GHz scale (1 ns = clock cycle of a 1 GHz processor); humans perceive change at ms scale.
How precise for very long durations?
JS doubles handle ~15 significant digits; converting 1 century to ns (~3.156e18) is at the edge of precision. For longer / more precise, use BigInt arithmetic.
Are leap seconds handled?
No — leap seconds (UTC adjustments ~once per year) are usually negligible for unit conversion. They matter for absolute time, not duration math.
How long is a "decade"?
10 years. By default uses Gregorian average year, so ~3652.4 days. Some calendar systems vary; this tool sticks to Gregorian.
Pro tips
- For software performance, stick to ns / µs / ms — humans-scale (s / min) introduces useless precision.
- For project work, use days for short, months for medium, years for long. Don't mix scales in one sentence.
- Use Gregorian average (365.2425 days) for long-term project math; calendar arithmetic ("13 months and 5 days") for legal contracts.
- For age, calendar arithmetic is more intuitive than "16,425 days old".
- Mental math: 1 minute = 60 s; 1 hour = 3600 s; 1 day ≈ 86,400 s; 1 year ≈ 3.15e7 s.
Reviewed by Ahsan Mahmood · Last updated 2026-05-06 · Part of ZTools.
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