CalculationProductivity Date & Time

Date Duration Calculator

Date Duration Calculator counts how many days fall between two dates the moment you enter them. Pick a start date and an end date and you get the total number of days, along with conversions into years, months, weeks, and hours and an exact "years / months / days" breakdown. Every result copies with one click.

Start date

End date

How to count days

Result

Enter a start date and an end date to see the number of days and unit conversions.

All calculations run entirely in your browser, and the dates you enter are never sent to a server.

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About Date Duration Calculator

There are two modes. "Days between" is the core duration calculation that tells you how many days lie from one date to another. "Add or subtract days" works the other way: it tells you which date falls a given number of days after or before a base date — handy for due dates, deadlines, and expiry dates.

You can choose how the days are counted. "Exclude end day" does not count the final day, so "today to tomorrow" is 1 day (the same way nights at a hotel or a countdown are counted). "Include both days" counts the start date as day one, so "today to tomorrow" is 2 days — the convention often used for event durations and legal time periods.

Conversions into years, weeks, and hours are derived from the total day count. The "years / months / days" breakdown is an exact calendar split that automatically accounts for leap days (February 29). The separate "years (approx.)" and "months (approx.)" figures divide the total days by an average year of 365.25 days, which is useful when you just want a rough span.

All calculations run entirely in your browser, and the dates you enter are never sent to a server. No signup or install required.

How to use

In "Days between" mode, enter a start date and an end date. Click a date field to pick from a calendar, or use the "Today" button to fill in today's date.
The total days, the years/months/days breakdown, weeks, and hours appear automatically. Use the copy button on each row to copy a value.
Choose "Include both days" to count the start date as well, or "Exclude end day" to leave the final day out.
To find a date a number of days after or before another, switch to "Add or subtract days", enter a base date and a number of days, and choose "After (+)" or "Before (−)".
The resulting date is shown with its weekday and can be copied.

Use cases

Checking how many days, or how many years and months, a contract, employment, or project period spans.
Seeing how many days remain until a deadline, due date, or payment date.
Counting days since an anniversary, length of service, or a birthday.
Counting an event or trip that includes the first day, using "include both days".
Finding the date that falls a set number of days after a base date (for example, a 90-day expiry).
Getting an accurate day count across periods that include a leap year.

Notes

"Exclude end day" leaves the final day out, while "include both days" counts the start date as well. The same two dates differ by one day depending on which you choose, so pick the one that matches your purpose.
The "years / months / days" breakdown is an exact calendar split and automatically accounts for differing month lengths and leap years.
"Years (approx.)" and "months (approx.)" divide the total days by an average year of 365.25 days (about 30.44 days per month), so they can differ from the exact breakdown.
If the end date is before the start date, the span is shown as an absolute value (without a minus sign).
In add/subtract mode, any fractional part of the number you enter is dropped and a whole number of days is used.
All calculations run in your browser; the dates you enter are never sent to a server.

FAQ

What is the difference between "include both days" and "exclude end day"?

It is how the days are counted. "Exclude end day" leaves the final day out, counting "today to tomorrow" as 1 day (like a countdown or hotel nights). "Include both days" counts the start date as day one, so "today to tomorrow" is 2 days. Event durations and legal time periods often use the inclusive count. You can switch between them with one tap.

Why do "years / months / days" and "years (approx.)" differ?

"Years / months / days" is an exact split based on the real calendar. "Years (approx.)" and "months (approx.)" instead divide the total days by an average year of 365.25 days (about 30.44 days per month) to give a rough figure. Because month lengths vary and leap years exist, the two can disagree.

Are leap years (February 29) taken into account?

Yes. The total days and the years/months/days breakdown are based on the actual calendar, so February 29 is counted correctly even for periods that span a leap year.

Can I calculate a date a number of days after or before another?

Yes. Switch to "Add or subtract days", enter a base date and a number of days, and choose "After (+)" or "Before (−)". The resulting date is shown with its weekday — handy for due dates and expiry dates such as 90 days out.

Can I count business days only, excluding weekends?

The current calculator counts calendar days (every day, including weekends and holidays). Counting business days (weekdays only) is not supported. As a guide, you can use the week count (total days divided by 7) or the breakdown.

Are the dates I enter sent to a server?

No. All day and date calculations happen entirely in your browser, so you can use it with confidence for work contract dates or personal anniversaries.