How to use this tool
Choose a starting date, enter a whole-number quantity and select days or weeks. Positive values move forward and negative values move backward. One week is exactly seven calendar days. The start date is day zero, so adding one day returns the following date. This tool does not skip weekends or holidays.
Try these values
Adding 30 days to January 1, 2026 gives January 31, 2026. Subtracting two weeks from January 15, 2026 gives January 1, 2026. Adding one day to February 28, 2028 gives February 29 because 2028 is a leap year.
The starting date is day zero
Adding one day means moving to the next date. Adding seven days means the same weekday one week later. This is useful for follow-ups, reminders and a rough project schedule, but a phrase such as “by the seventh day” may follow a different counting convention. If both boundary dates are meant to count, check the interval with the date duration calculator.
Calendar days do not skip closures
A result can land on a weekend or a public holiday. The tool does not move that result to the next business day, because different organizations use different adjustment rules. Check the returned weekday and the relevant holiday list before treating it as a working deadline. Negative values work the same way in reverse, including across February and the end of a year.
Common questions
Can I subtract days?
Yes. Enter a negative number to move backward.
Does it skip weekends?
No. It adds calendar days. Use the business days calculator to count workdays in a range.
Are leap years handled?
Yes. The calculation uses the Gregorian calendar, including century leap-year rules.
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