Add or Subtract Days Calculator
What date is 90 days from today? Add or subtract days, weeks, months or years to any date and see the day of the week you land on.
Days and weeks are added as exact multiples of 24 hours at UTC.
How the add or subtract days calculator works
Days and weeks are added as exact multiples of 24 hours at UTC. Months and years are added calendar-wize: 31 January plus one month gives 28 (or 29) February, the last day of the shorter month, which is the convention used by most contracts and spreadsheets.
Formula: result = start + n × unit
Worked examples
| Inputs | Result date | Note |
|---|---|---|
| 90 days after 2026-01-01 | Wednesday 1 April 2026 | 1 April 2026 |
| 1 month after 31 January 2026 | Saturday 28 February 2026 | 28 February 2026 |
| 10 business days after 2026-06-01 | Monday 15 June 2026 | 15 June 2026 |
FAQFrequently asked questions
What is 30 days from today?
Enter today's date and 30 days; the calculator gives the date and its weekday.
What happens when I add a month to the 31st?
You land on the last day of the next month — 31 March + 1 month = 30 April.
How are business days counted?
Weekends are skipped; public holidays are not (they vary by state).
Can I subtract?
Yes — enter a negative amount.
Why do some contracts say "calendar days"?
To make clear that weekends count; "business days" or "working days" exclude them.
Where these figures come from
- ISO 8601 — Date and time — Representations for information interchange — the yyyy-mm-dd format and the week-numbering rules used here
- US Naval Observatory — Calendars — the Gregorian leap-year rule
- US Office of Personnel Management — federal holidays — federal holidays (not applied here)
Last checked: September 2026. The Gregorian calendar rules do not change; working-day counts exclude Saturdays and Sundays only.