Date Calculator
Pick a starting date, choose how much time to add or subtract, and get the resulting date instantly.
Overview
Manually counting forward or backward across month boundaries is error-prone, especially with months of different lengths or a leap year in the range. This tool applies calendar-aware arithmetic — adding a month to January 31st correctly lands on the last day of February rather than overflowing into March — so the result matches how a calendar actually works, not a naive day-count approximation.
Examples
Add months
2026-01-31 + 1 month
Saturday, February 28, 2026
Subtract days
2026-08-15 − 45 days
Sunday, July 1, 2026
How It Works
- Enter the starting date.
- Choose Add or Subtract.
- Enter the amount and pick a unit — days, weeks, months, or years.
- The resulting date, with its day of the week, appears instantly.
Use Cases
Deadline planning
Find the date 90 days from a contract signing, or 6 months before a renewal date.
Recurring events
Work out the date of a recurring event a set number of weeks or months out.
Tips
- Adding months to a date near month-end (like the 29th–31st) clamps to the last valid day of the target month rather than rolling over.
FAQ
No. The calculation runs entirely in your browser using JavaScript.
Yes. Date arithmetic uses the browser's native calendar handling, which correctly accounts for leap years.