Date Add / Subtract Calculator
Add or subtract years, months, weeks, and days from any starting date
Calculation Result
Resulting Target Date
Thursday, December 31, 2026
ISO Format: 2026-12-31Day of Week
Thursday
Operation
Future
How this calculator works
1
Select starting reference date.
2
Choose Add or Subtract operation.
3
Input numbers for years, months, weeks, or days to find the resulting target date.
Formula & Mathematics
Date Offset Calculation
TargetDate = StartDate ± (Years + Months + Weeks + Days)
Accurately adjusts month ends (e.g., adding 1 month to January 31 lands on February 28/29).
Worked Example
Adding 90 days to October 1, 2024
90-day deadline project.
• October: 30 remaining days
• November: 30 days
• December: 30 days ⟹ Lands on December 30, 2024
Target date is Monday, December 30, 2024.
Frequently Asked Questions
The date automatically clamps to the last valid day of that target month.
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