How to use this tool
Select a start and end date. By default, the start is included and the end is excluded: January 1 to January 2 is one day. The end-date option adds one day to the interval. Calendar months are counted with month-end clamping, while total days are counted independently using UTC calendar dates. For workdays and custom weekends, use the business days calculator.
Try these values
January 1 to January 31, 2026 is 30 days, or 4 weeks and 2 days. Including the end date makes it 31 days. Calendar months have different lengths, so 30 days does not always equal one month.
A duration and a list of dates are different
Think of walking from one midnight to the next. January 1 to January 2 crosses one full day, even though two dates are written down. That is why the default excludes the end date. If you are counting attendance, leave or an event covering both named dates, including the end may be more useful. Check the rule before changing the option just to match an expected number.
Use the right result for the task
Total days are useful for comparing fixed intervals. Calendar years and months are useful for describing anniversaries or a long project in familiar terms. Weeks and leftover days can help with schedules. None of these automatically means business days. For work deadlines, open the business days calculator and enter the weekend pattern and holiday dates that apply to the organization involved.
Common questions
Are both dates counted?
The start date is counted and the end date is excluded by default. Select Include end date to count both.
Does daylight saving affect the answer?
No. This tool compares calendar dates, not local clock hours.
Can I subtract dates in reverse order?
The end must be on or after the start. Swap your dates to find the positive duration.
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