➕ Date Add / Subtract Calculator
"What date is 90 days from today?" — pick a start date, add or subtract days, weeks, months or years, and see the result with its weekday.
90 days after July 18, 2026 is
Friday, October 16, 2026
Months clamp to month-end: 31 Jan + 1 month = last day of February.
How the date add / subtract calculator works
Days and weeks are exact arithmetic. Months and years follow the calendar convention: the day-of-month is preserved where possible and clamped to the month's end where not — 31 January + 1 month gives 28 (or 29) February, not 2 or 3 March. That matches how billing cycles, notice periods and subscriptions roll dates.
The month-clamping rule is where hand-counting goes wrong most: "three months from 30 November" is 28 February, not 2 March. Deadlines defined in days (e.g. "within 30 days") and in months ("one month's notice") can differ by a day or three — check which your contract actually says.
Frequently asked questions
What does adding a month to 31 January give?
The last day of February — the 28th or 29th. The convention preserves the day-of-month and clamps to the target month's end when it doesn't exist, which is how billing and legal date rolls work.
How do I subtract days instead of adding?
Switch the direction toggle to "before" — the same arithmetic runs backwards, e.g. 45 days before a deadline for a reminder date.
Is "30 days" the same as "one month"?
No — months are 28 to 31 days long, so a 30-day deadline and a one-month deadline diverge for most start dates. Use the unit your document specifies.
Does the result account for leap years?
Yes — the browser's calendar arithmetic knows every leap day. Adding one year to 29 February 2024 clamps to 28 February 2025.
Does this run locally?
Yes — pure calendar arithmetic in your browser; nothing is sent anywhere.