Date Duration Calculator: Days Between Dates and Weekdays

How many days are there between two dates? The answer depends on whether you count the start date, the end date, or only the time between them. A second question is how many of those days fall on the working days of your locale.

The Sikelia Tools Date Duration Calculator calculates elapsed calendar days, counts weekdays according to the selected region, lets you optionally include the end date, and provides a separate field to add or subtract calendar days. It runs in the browser without requiring registration.

Find the number of days between two dates

1. Open the calculator and locate the start and end date fields.
2. Select two valid calendar dates. The calculation updates when you change them.
3. Read the result for Days. By default, the duration counts the days elapsed from the start date without additionally including the final date.
4. Select Include end date when both endpoints should count, as they might in a schedule of dates on which an activity takes place.
5. Look at Weekdays for the number of working days using the calculator’s applicable weekend rules.

For example, from Monday, November 2, 2026, to Friday, November 6, 2026, the normal elapsed duration is 4 calendar days. Including the end date produces 5 calendar days. In a Monday–Friday workweek the weekday count follows the same endpoint selection.

Calendar days and weekdays are different

Calendar days include weekends. Weekday counts use a workweek convention, and that convention can vary by market. The Sikelia calculator adapts the displayed workday label and regional weekend settings rather than assuming the same weekend everywhere.

A weekday is not necessarily a working day for your particular employer, and the tool does not subtract public holidays or personal leave. To calculate business deadlines, check the country, local holidays, time-of-day rules and the agreement that defines the deadline.

For project planning, you might use total calendar days for an elapsed interval and weekdays for a rough estimate of office availability. Do not substitute one for the other without checking what the task actually requires.

How to add or subtract days from a date

The calculator includes a separate Add days field. Enter a positive whole number to move forward from the start date, or a negative number to move backward. Its result is a calendar date: it is not a promise that a shipment or other external process will finish on that day.

This can help you identify the date 14 calendar days after a project starts, move a planned reminder, or compare milestones across months. Because months and leap years have different lengths, letting the calculator handle date arithmetic is safer than assuming every month has 30 days.

Inclusive dates: when do you count the final day?

An inclusive interval includes both the opening and closing dates. For example, an event advertised as running November 2 through November 6 spans five listed calendar dates even though the elapsed difference between the two date boundaries is four days.

If you are checking a legal, tax, financial or contractual deadline, the rules governing inclusion may differ. This article explains the tool’s calendar arithmetic, not how a particular authority counts a deadline.

Useful checks before sharing the result

Confirm that you entered the dates in the intended order and selected the appropriate calendar representation. Check whether you need calendar days or weekdays, and whether the endpoint is inclusive.

If you instead want to calculate somebody’s age in years, months and days, use the Age Calculator and see the age calculation guide. Age and date-duration calculations answer related but different questions.

Try the example yourself in the free Date Duration Calculator to see how the results change when you include the end date.