Time Duration CalculatorFree online other calculator — instant results, no sign-up
Duration between two dates.
About the Time Duration Calculator
The Time Duration Calculator computes the exact calendar span and total elapsed time between two selected dates. It converts the interval into a breakdown of years, months, and days, alongside total counts for days, weeks, and hours. This tool is useful for project scheduling, tracking milestones, calculating age, and event planning.
- Start
- The beginning date of the interval in YYYY-MM-DD format.
- End
- The concluding date of the interval in YYYY-MM-DD format.
Formula and method
Days = EndDate - StartDate Years, Months, Days = Calendar difference (accounting for month lengths) Weeks = Days / 7 Hours = Days × 24
- DaysTotal integer count of calendar days between Start and End
- Years, Months, DaysDecomposed calendar duration based on actual calendar month lengths
- WeeksTotal days divided by 7, rounded to 2 decimal places
- HoursTotal days multiplied by 24 hours per day
The calculator first evaluates the absolute calendar difference between the two dates to determine total days elapsed. It then computes the breakdown of full years, remaining full months, and leftover days using standard calendar progression. Finally, total weeks are derived by dividing total days by 7 (rounded to two decimal places), and hours are calculated by multiplying days by 24.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Start1970-01-01
- End1970-04-11
Results
- Duration0 years 3 months 10 days
- Days100
- Weeks14.29
- Hours2,400
How to use the Time Duration Calculator
- 1Enter or select the starting date.
- 2Enter or select the ending date.
- 3Evaluate the calendar year, month, and day increments separating the two dates.
- 4Calculate the total elapsed days, convert days to weeks by dividing by 7, and compute hours by multiplying by 24.
Reading your result
The primary 'Duration' output gives a natural-language breakdown showing elapsed full years, remaining months, and remaining days. The remaining metrics give cumulative totals across identical durations: total whole days, weeks expressed with two decimal places, and total equivalent hours assuming 24-hour days.
Limitations
The calculation operates strictly on full calendar dates and does not accept specific times of day, minutes, or seconds. It also assumes standard 24-hour days for the hour calculation, ignoring Daylight Saving Time transitions or leap seconds.
Common questions
Does the calculator include both the start date and end date?+
It measures the elapsed duration between midnight of the start date and midnight of the end date. To count both dates inclusively (for example, counting both day 1 and day 2 as two full working days), add one day to the result.
How does the tool handle leap years?+
The calendar day count and the year/month/day decomposition use full calendar logic, which automatically includes February 29 when the date range crosses a leap year.
Can I calculate backwards if the end date is earlier than the start date?+
The underlying date functions measure the difference between the two points in time; selecting an end date prior to the start date will measure the negative span or absolute difference between those dates.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.