Add or Subtract Days Calculator

What date is 30, 60 or 90 days from now? Add or subtract days from any date.

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About this calculator

"Payment due within 90 days", "valid for 180 days", "6 weeks from today" — this calculator adds or subtracts any number of days from a date and tells you the exact day of the week it lands on, so a deadline never surprises you on a Sunday.

The formula

Result = Start date ± N days (calendar)

Worked example

90 days after 18 July 2026 is Friday 16 October 2026.

Common mistakes

Adding working days as calendar days — a 30-working-day deadline is about 6 weeks, not 30 days.
Anchoring to the wrong start date (invoice date vs delivery date changes everything).
Forgetting that a deadline landing on a weekend usually rolls to the next working day — check the contract wording.

Frequently asked questions

Convert to days for exactness, or note that "one month from the 31st" is ambiguous — many contracts specify days precisely to avoid this.

Use the Business Days calculator for Mon–Fri counting; this tool counts every calendar day.

No — it reports exactly where the date lands, including the day name so you can see if it's a weekend.

Assumptions & limitations

Calendar-day arithmetic including weekends and holidays.

Sources & verification

This calculator applies the standard formula published above to the figures you enter — it relies on no external statutory data. The formula and the worked example were checked by hand against each other.

Formula last verified: 24 July 2026

Maintained by: Steve Davis, Founder & Editor — see our editorial standards

Spotted an error or an out-of-date figure? Report it — corrections are prioritised over all other work (see our corrections policy).