Add Days to Date
Find out what date it will be after adding or subtracting days.
Start date
Days to add (negative to subtract)
30 days after 2026-05-15
June 14, 2026
Sunday
Why adding days matters
Adding 30 days to Jan 31 gives Mar 2. Adding 1 month is ambiguous — February has 28 or 29 days. Day-based arithmetic is unambiguous.
- +14 days: standard return window
- +30 days: net-30 payment terms
- +90 days: quarter-end deadlines
- Negative days: subtract from date
What this tool does
Calculates what the date will be after adding or subtracting a number of days from a starting date. Quick preset buttons for common intervals.
Input fields explained
Start date
The reference date you are calculating from. Defaults to today.
Days to add
Number of days to add. Use a negative number to go backwards in time. For example, -30 gives the date 30 days ago.
💡 Tips & context
→Use this to calculate payment due dates, project deadlines, subscription end dates, or warranty expiry.
Formula / How it works
result = start + (days × 86,400,000 ms). Negative values subtract days.