Date Addition & Subtraction Calculator
Need to know what date is 90 days from today or what day it was 6 weeks ago? This tool performs calendar arithmetic while automatically accounting for month lengths and leap years.
Calculated Result
Enter values to view result
Formula & Mechanics
Target Date = Base Date ± (Days / Weeks / Months)
Adjusts the calendar date object by the specified interval and recalculates the Gregorian calendar day of the week.
Worked Step-by-Step Example
Scenario: Add 45 days to October 1, 2026.
- October has 31 days (30 remaining)
- November has 30 days
- 30 + 15 = 45 days ⟹ November 15, 2026
The result is Sunday, November 15, 2026.
Frequently Asked Questions
Does this handle year rollover?
Yes, adding days that cross December 31 will advance into subsequent calendar years seamlessly.
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