Date Add & Subtract Calculator
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Add or subtract days, weeks, or months from a start date — calendar math, not business days.
Start date & interval
Result date
2026-08-30
Added 30 days from 2026-07-31
- Day of week
- Sunday
Related calculators
Adding and subtracting dates
To shift a calendar date forward or backward, add the interval to the day, week, or month count. Weeks are exact multiples of seven days. Months follow calendar months — adding one month to January 31 gives February 28 or 29, not March 3.
This tool uses calendar arithmetic, not business days. Weekends and holidays are included unless you use the business-days calculator. For legal deadlines that say "30 calendar days," count from the day after the event unless your policy says otherwise.
Example: starting March 15, 2026 and adding 45 days lands on April 29, 2026. Subtracting 3 months from July 31, 2026 gives April 30, 2026 — month-end dates adjust to the last valid day of the target month.
Common questions
Does adding months account for different month lengths?
Yes. JavaScript calendar months handle 28–31 day lengths automatically. Adding one month to January 31 becomes February 28 or 29, not March 2.
Is this the same as business days?
No. This calculator counts every calendar day. Use the business-days calculator to skip weekends.