About the Time Converter
This time converter turns a duration expressed in one unit into any other, across milliseconds, seconds, minutes, hours, days, weeks, months and years. It is built for durations rather than dates, which is an important distinction: it answers how long is 90,000 seconds, not what date falls 90,000 seconds from now. For consistency and predictability a month is treated as exactly 30 days and a year as exactly 365 days, so calendar irregularities such as February and leap years are deliberately left out of the arithmetic.
How to use the Time Converter
- 1
Enter the duration you want to convert in the Value box.
- 2
Pick the unit it is currently expressed in under From.
- 3
Pick the unit you want under To.
- 4
Read the converted duration, and check the table to see it in every unit including milliseconds.
What people use it for
Configuring timeouts and cache lifetimes
Systems want seconds or milliseconds while humans think in hours. A 24 hour cache lifetime is 86,400 seconds, and a 30 day cookie is 2,592,000 seconds.
Project and capacity planning
Turning 320 hours of estimated effort into 8 working weeks at 40 hours makes a plan legible to people who do not think in hours.
Interpreting logs and benchmarks
A job that ran for 5,400,000 milliseconds took 90 minutes, or 1.5 hours. Converting once makes performance regressions easier to talk about.
How the units are defined here
The chain is fixed and exact for everything up to a week. A second is the base, a minute is 60 seconds, an hour is 3,600 seconds, a day is 86,400 seconds and a week is 604,800 seconds. Above that, real calendars stop cooperating, so this tool adopts the common convention of a 30-day month at 2,592,000 seconds and a 365-day year at 31,536,000 seconds. Be aware of what that costs you. Real months run from 28 to 31 days, so a 30-day month is up to 3.3 percent adrift from a specific calendar month, and twelve of them make 360 days rather than 365. The average Gregorian year is 365.2425 days, chosen to track the tropical year of about 365.2422 days, which is why we insert a leap day in years divisible by four except centuries not divisible by 400. If you need the number of days between two actual dates, or a date shifted by a number of months, use a date calculator instead — the answer depends on the calendar, not on a fixed factor.
Seconds, timestamps and the end of leap seconds
Since 1967 the second has been defined by atomic physics: exactly 9,192,631,770 periods of the radiation from the hyperfine transition of the caesium-133 ground state. That definition is entirely independent of the Earth's rotation, which is gradually and irregularly slowing. To keep civil time aligned with the planet, leap seconds have been inserted into UTC 27 times since 1972, most recently at the end of 2016. Because they arrive at short notice and produce a 61-second minute, they have caused repeated outages in software that assumed every minute has 60 seconds, and in 2022 the General Conference on Weights and Measures resolved to stop inserting them by 2035. Unix time sidesteps the problem by counting seconds since 1 January 1970 UTC while pretending leap seconds do not exist. JavaScript and many web APIs use the same epoch but count in milliseconds, which is why timestamps from a browser are a thousand times larger than those from most backend systems — dividing by 1,000 converts between them.
Tips
- A day is 86,400 seconds and a 365-day year is 31,536,000 — worth memorising, as they underpin most timeout maths.
- A standard work year is often taken as 2,080 hours, being 40 hours across 52 weeks before leave and holidays.
- For anything involving actual dates, time zones or daylight saving, use a date calculator rather than a fixed-factor conversion.