Date arithmetic

Add or subtract dates

Move a date by calendar units. Years are applied first, then months, then weeks and days; invalid month-end dates clamp to that month’s final day.

Result

Friday, October 9, 2026

Added to Wednesday, September 9, 2026.

ISO date2026-10-09

WeekdayFriday

Absolute day distance30

Month-end clamping happens after years and again after months. For example, subtracting one month from March 31 lands on February 28 or 29.