From milliseconds in a performance benchmark to years in a long-term project, time spans stretch across a huge range of units, this converter handles all of them in one tool.
How to use this time unit converter
- Enter a value and select your From unit (milliseconds, seconds, minutes, hours, days, weeks, months, or years).
- Select your To unit.
- Read the converted result instantly, or tap Swap Units to reverse the direction.
What this converter does
This tool converts between milliseconds, seconds, minutes, hours, days, weeks, months, and years. Months and years use average calendar lengths, 1 month is approximately 30.4368 days, and 1 year is 365.25 days (accounting for leap years), since calendar months vary in length and can’t be represented by one exact figure.
1 year ≈ 365.25 days (accounting for leap years)
1 month ≈ 30.4368 days (average calendar month)
Why months and years use approximations
Unlike seconds, minutes, hours, days, and weeks, which have fixed, exact relationships to each other, calendar months vary from 28 to 31 days and years vary between 365 and 366 days due to leap years. This converter uses averaged values (365.25 days per year, roughly 30.44 days per month) to give a consistent, sensible conversion, rather than requiring you to specify an exact calendar date range.
Frequently asked questions
Why isn’t a month exactly 30 days in this converter?
Calendar months vary from 28 to 31 days depending on which month and whether it’s a leap year, so this converter uses the average calendar month length (about 30.44 days) rather than a fixed 30, giving a more accurate long-run conversion.
Why does a year equal 365.25 days here instead of 365?
365.25 accounts for leap years, which add an extra day roughly every 4 years, using this average gives a more accurate conversion for durations spanning multiple years than a flat 365 would.
