About this tool
Compute the date that is N days before or after a given date. Negative N subtracts.
Formula
result = startDate + N days, using calendar arithmetic that handles leap years.
Worked example
2026-01-01 + 30 days = 2026-01-31 (Saturday).
Notes
Adding 365 days does not always land on the same calendar date the next year — leap years offset by one day.