Add Days to Date Calculator
Add or subtract a number of days from a start date to find a future or past date. Useful for planning deadlines and event dates.
Add or Subtract Days from a Date
How the Calculation Works
How It Works: Enter a start date and a whole number of days to add. Use a negative number to subtract days. The result is calculated by shifting the date by that many 24-hour days; this tool does not add calendar months or weeks as separate units.
Worked Example
Example: Start date September 1, 2026; add 90 days:
- Result: November 30, 2026
To count back 15 days from September 1, enter -15; the result is August 17, 2026.
How to Use This Calculator
Uses: Find a date a set number of days before or after a starting date—for example, a project deadline or event date. This tool shifts by days, not by calendar months, and does not account for business days or holidays.
Frequently Asked Questions
How do I add days to a date?
Enter your start date and a whole number of days to add. The calculator shows the resulting date.
Can I subtract days?
Yes. Enter a negative number of days; for example, -7 moves the date back seven days.
Can I add calendar months with this calculator?
No. This tool adds or subtracts days only. A month does not have a fixed number of days, so use a calendar if you need to move by calendar months.