How is this different from 'Date Difference'?

Date Difference takes two dates and returns the gap between them. Date Add/Subtract takes one date and a duration and returns a new date — the inverse operation.

How are month additions handled?

Adding months keeps the same day of the month when possible. If the target month has fewer days (e.g., Jan 31 + 1 month), the result rolls to the last day of the shorter month (Feb 28/29).

Does it handle leap years?

Yes. JavaScript's Date object respects leap years, so Feb 29 + 1 year rolls to Feb 28 on non-leap years.

Can I count business days instead of calendar days?

Not here — use the separate Working Days Calculator. This tool counts every day including weekends.

Date Add / Subtract Calculator

Date & Time· 10 tools

Free date add/subtract calculator. Enter a start date and the number of days, weeks, months, or years to add or subtract. We return the resulting date with its weekday. Handy for contracts, deadlines, pregnancy tracking, membership expiries, and any 'X days from today' question.

Start date

Direction

Amount

Unit

Resulting date

Friday, May 22, 2026

2026-05-22

Weekday

Friday

Calendar days offset

+30

Frequently Asked Questions

References

Date and time — MDN reference — Mozilla Developer Network

Related Tools

Date Difference Calculator
Calculate the exact number of days, weeks, months, and years between two dates.
Working Days Calculator
Count business days (Mon-Fri) between two dates, or add/subtract working days from a start date.
Countdown to Date
Live countdown to any future date — days, hours, minutes, and seconds updated in real time.

Frequently Asked Questions

References and sources

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