Add Months and Years to a Date

Calendar month arithmetic is not a fixed number of days. This calculator applies years, then months, then days, and clamps overflowing day numbers to the last valid day of the landing month.

Start Date Years to add or subtract Months to add or subtract Days to add or subtract

Order: years → months → days. Negative values move backward.

Original date:

Adjustment sequence:

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Weekday of result:

Clamp examples built into the code

January 31, 2025 + 1 month = February 28, 2025
January 31, 2024 + 1 month = February 29, 2024
February 29, 2024 + 1 year = February 28, 2025

JavaScript’s default month overflow (January 31 plus one month becoming March 3) is not used. The clamp is deliberate. If the final date leaves 1900–2100, you see an error instead of a wrapped year.

Months, years, and leap days · Add calendar days