Add or Subtract Days Calculator
Add or subtract any number of days from a start date to find the new date and weekday.
Start date
days
Sat Jul 18 2026 (Saturday)
Sat Jul 18 2026
2026-07-18
Saturday
30
Formula
Examples
| Input | Result |
|---|---|
| Start 2026-01-31, add 1 day | 2026-02-01 (Sunday) |
| Start 2026-03-01, subtract 1 day | 2026-02-28 (Saturday) |
About this calculator
The add or subtract days calculator shifts a start date forward or backward by a whole number of days. Enter a positive value to move into the future or a negative value to move into the past. The result shows the new calendar date in both a readable and ISO format, along with the weekday it lands on.
This is useful for due dates, deadlines, rental and return dates, prescription refills, warranty windows and any rule expressed as "N days after" or "N days before" a known date. Because it works on real calendar days, month lengths and leap years are handled automatically.
Frequently asked questions
Enter a negative number, such as -14, in the "Days to add" field. The result moves backward from the start date.
No. Adding 1 day to a Monday gives Tuesday; the start date itself is day zero.
The day count is rounded toward zero to whole days, since calendar dates are whole-day units. For partial days use the Time Duration Calculator.
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