Calendar Calculator: Add or Subtract Days, Weeks, Months

Perform advanced calendar math: add or subtract years, months, weeks, and days from any date. Find the day of the week and calculate date differences.

Calendar Calculator

Years
Months
Weeks
Days
Result Date
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Day of the Week
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Difference
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Month Math Explained

When adding months, if the target month has fewer days (e.g., adding 1 month to Jan 31), standard rules typically shorten the result to the last day of that month (Feb 28/29).

$$ \text{Date}_{\text{new}} = \text{Date}_{\text{old}} \pm \text{Offset} $$

FAQ

How are leap years handled?

Our calculator automatically accounts for leap years. Adding 1 year to Feb 29, 2024 results in Feb 28, 2025.