Date Calculator

Count days between dates, or add and subtract days from a date.

Choose the two dates and decide whether both endpoints should count. For a deadline offset, switch to adding or subtracting days from a starting date.

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How to use

Count calendar days for a plan

Count days between dates, or add and subtract days from a date.

Step by step

Provide the source using: Start date / End date.
Set: What would you like to calculate? / Number of days / Include both start and end dates. Use the reference below to choose the options that fit your task.
Choose: Calculate. Inspect the result before copying, downloading or using it elsewhere.
Choose the two dates and decide whether both endpoints should count. For a deadline offset, switch to adding or subtracting days from a starting date.

Choosing the settings

Option	What changes
Include both start and end dates	The default result is the end date minus the start date. For example, February 28 to March 1 in a leap year is 2 days apart, or 3 days including both endpoints. If the end date is earlier, the result is negative. Inclusive counting increases the absolute day count by one.
Number of days	No. This tool works with Gregorian calendar dates, not hours or timestamps. It supports years 0001 to 9999. It does not count business days or public holidays and does not approximate months as 30 days.

Example and expected result

September 16 to September 20 is 4 days apart, or 5 days when both dates count. These are calendar days, including weekends. Business-day rules and public holidays need a different calculation.

If it is not working

If a day count looks wrong, check the start/end order and whether both endpoints are included. For a deadline, confirm whether the rule asks for calendar or business days; this tool does not exclude weekends or holidays.

How are days counted?

The default result is the end date minus the start date. For example, February 28 to March 1 in a leap year is 2 days apart, or 3 days including both endpoints. If the end date is earlier, the result is negative. Inclusive counting increases the absolute day count by one.

Will timezones or daylight saving change the answer?

No. This tool works with Gregorian calendar dates, not hours or timestamps. It supports years 0001 to 9999. It does not count business days or public holidays and does not approximate months as 30 days.