Date CalculatorAdd & Subtract Dates
Determine the exact date after a certain number of days, weeks or months.
Easily add or subtract days, weeks or months from a start date. This tool is ideal for accurately determining delivery dates, project milestones, or legal notice periods.
Add & subtract dates: determine deadlines reliably
Adding or subtracting adds or removes a number of days, weeks, months or years from a start date. The result is a concrete calendar date including the weekday – ideal for delivery dates, project milestones and legal deadlines.
How the first day is treated matters. For an "from today" calculation the calculator uses today as day 0 and counts forward. In many legal contexts the day of the triggering event is excluded and the period starts the next day, so always check the convention that applies to your deadline.
When adding months, month length matters: if the target day does not exist (for example the 31st in a shorter month), the result rolls back to the last day of that month. The calculator applies these rules automatically, so the result stays correct across leap years too.
Frequently asked questions
Is today counted in the deadline?
For an "from today" calculation, today is treated as day 0 and the days are counted forward. Legal deadlines often start on the day after the triggering event, so verify the rule that applies to you.
What happens at the end of a month?
If the target day does not exist in the target month (e.g. the 31st in February), the result is rolled back to the last valid day of that month.
Can I calculate backwards?
Yes. Using a negative value or subtraction returns a date in the past – useful for finding when a period started, counting back from a fixed date.
Are weekends skipped?
No, calendar days including weekends are added. For working days only, use the business-day calculator.