Date Difference and Countdown Calculator
Calculate the number of days between two dates, including the start and end dates.
Input
The example value has been entered. Check it immediately or change the value.
Input is processed in the browser. Refreshing returns a sample value.
Result
Check or change the value using the example value result.
Calendar dates are calculated without time zone changes. Enter valid dates between 1900 and 2100.
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Calculation·conversion criteria
Calculate the number of days between two dates, including both start and end dates.
Input example
October 2–12: 10 days difference, 11 days including both ends
From 2026-10-02 to 2026-10-05, the time difference is 3 days, including both ends, totaling 4 days. Choose the result that fits your purpose, like the number of stays or attendance days.
How to use
- Use the entered example value or change the start date and end date items.
- Click Verify result and check the following result.
- Result can be copied if needed.
Frequently Asked Questions
What if start and end dates are the same or in reverse order?
The same day has a difference of 0 days and 1 day of included days. If the end date comes before, the date difference is negative; the end includes both ends, resulting in a positive number of days unrelated to direction.
Does the time zone cause differences in dates?
This tool calculates the difference between calendar dates without visual cues. Do not use it for calculating actual elapsed time, including flight time or summer time.
Calculation criteria and reference materials
The calculation formula and scope of this tool are disclosed in the above description. Examples can be checked by substituting input values into the formula or following the specified string and calendar handling rules.
Verification of calculation criteria: · Calculation·verification principles · Report errors