Date math · Add or subtract

Date ± Days Calculator

Add or subtract days, weeks, months, or years from any starting date.

To add days to a date, count forward across months, accounting for month lengths and leap years. 90 days after March 1, 2026 is May 30, 2026. Choose add or subtract and enter the number of days above.

Add or subtract from a date

Starting date

Sign

Amount

Unit

Resulting date

—

ISO format—

Day of year—

Week number—

How to use this calculator

Set a starting date, choose a sign (add or subtract), enter an amount, and pick a unit (days, weeks, months, years, or business days). The result updates instantly.

Common use cases

SLA deadlines: "5 business days from order date"
Court deadlines: "20 days to respond to a complaint"
Trial periods: "30 days from signup expires on..."
Pregnancy due date: "40 weeks from last menstrual period"
Subscription renewal: "1 year from purchase date"
Quarantine end: "10 days from exposure"

Calendar edge cases

Adding a month to the 31st of a month gives the last day of the next month when it has fewer days. For example, January 31 + 1 month = February 28 (or 29 in leap years). This matches how most calendar apps and human intuition work.

Questions, answered

Things people actually ask.

Enter the starting date and the number of days to add. The calculator returns the resulting calendar date, accounting for varying month lengths and leap years. Use negative numbers to subtract.

Yes — toggle 'Business days only' to skip weekends. Useful for SLA calculations, court deadlines, and project planning where weekends don't count.

Calendar-aware. If you add 1 month to January 31, you get February 28 (or 29 in a leap year), since February doesn't have a 31st. If you add 1 year to Feb 29, you get Feb 28 in non-leap years.

More time tools.

Sources & standards

Where these answers come from

The figures, rules, and standards on this page are based on the official sources below. This information is provided for general reference only and is not legal, financial, or medical advice.