Date Calculator
Days between two dates, add or subtract time from a date, or count business days only.
How to use the date calculator
- Pick a mode. “Days between dates” compares two dates; “Add or subtract” moves a date forward or back.
- Fill in the dates. Use the pickers or type YYYY-MM-DD. For “between” mode, order does not matter.
- Set the options. Toggle inclusive counting or business-days-only for the between mode; choose the amount, unit, and direction for add/subtract.
- Press Calculate. The answer shows the day count or resulting date, with the weekday of each date involved.
Frequently asked questions
What is the difference between inclusive and exclusive day counts?
Exclusive counts the days strictly between the two dates: January 1 to January 3 is 2 days. Inclusive counts both endpoints as well: January 1 to January 3 is 3 days. Project plans usually want inclusive; durations usually want exclusive.
How are business days counted?
Monday through Friday only — Saturdays and Sundays are skipped. Public holidays are not excluded, because they vary by country.
What happens when I add a month to January 31?
The result lands on the last valid day of the target month: January 31 plus one month is February 28 (or February 29 in a leap year). This matches how most date libraries behave.
Do daylight-saving changes affect the day count?
No. All math is done in UTC, so a 23-hour or 25-hour DST day still counts as exactly one day.
Is my data sent anywhere?
No. Every calculation happens in your browser; nothing you type is sent to a server or stored.
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