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.
Tuesday, September 9, 1980
Added to Sunday, August 10, 1980.
ISO date1980-09-09
WeekdayTuesday
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.