Units run in order
The calculator applies years first, then months, then weeks and days. A mixed adjustment can differ from repeating several smaller calculations in another order.
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.
Saturday, October 24, 2026
Added to Thursday, September 24, 2026.
ISO date2026-10-24
WeekdaySaturday
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.
Date-shifting rules
How calendar arithmetic is applied
Month ends clamp safely
January 31 plus one month lands on February 28 in a non-leap year, or February 29 in a leap year. The result stays inside the requested month.
Leap-day anniversaries
February 29 plus one year becomes February 28 when the result year is not a leap year. Subtraction follows the same last-valid-day rule.
Weeks are seven days
One week always adds or subtracts seven calendar days, preserving the weekday when no other units are entered. Two weeks is exactly 14 calendar days.
Calendar days include weekends
Days and weeks count every calendar date, including weekends and holidays. For a deadline that skips non-working days, use the business-days calculator.
Measure the resulting span
The absolute day distance summarizes how far the result moved. Use the days-between calculator when you also need inclusive counting, weekdays, or a years-months-days breakdown.