Time Conversion Calculator

Converting Time Units Means Converting Through Seconds

Seconds, minutes, hours, and days convert cleanly because they're fixed and exact. Months, years, and decades don't have a single fixed length — a month can be 28 to 31 days, and a year is 365 or 366 — so any calculator that converts between them has to pick a defined average. This one uses the mean Gregorian calendar year (365.2425 days, which is what makes the leap year rule work out over the long run) as the basis for month, year, and decade conversions, converting every unit through seconds as a common intermediate.

The Formula

Reference Conversion Factors

Month, year, and decade figures are averages based on the Gregorian calendar's mean year length — useful for estimation, but not exact for any single specific month or year.

A Worked Example

Converting 2.5 years into days: 2.5 × 31,556,952 seconds ÷ 86,400 seconds = 913.10625 days.

Where This Calculation Matters

• Estimating long durations — converting a multi-year figure into days or weeks for scheduling purposes, where an average-length year is an acceptable approximation.
• Comparing measurements — putting durations quoted in different units (a warranty in years, a rental period in weeks) onto a common scale.
• Quick unit sanity checks — converting seconds or minutes from a technical measurement into more intuitive hours or days.

How to Use This Calculator

1. Enter the value to convert.
2. Select the unit to convert from.
3. Select the unit to convert to.
4. Select Calculate to see the converted value.

Related Calculations

For an exact duration between two specific timestamps rather than a unit conversion, see the Time Duration Calculator. To find the exact days between two calendar dates, use the Day Counter.