What this date calculator does
It answers questions such as "what is the date 90 days from today?", "what was the date 6 weeks ago?" or "when is my due date if the contract runs 18 months from signing?". Enter a start date, choose add or subtract, and fill in any combination of years, months, weeks and days. The tool applies the calendar months and years first, then the weeks and days, and shows the resulting date with the weekday.
How months and leap years are handled
Months have different lengths, so adding one month to 31 January does not land on a real date in February. The convention used here, and by most calendar software, is to keep the same day number when possible and otherwise use the last day of the target month. Adding one month to 31 January 2026 gives 28 February 2026, while adding it to 31 January 2028 gives 29 February 2028 because 2028 is a leap year. Days and weeks are exact: 7 days always equal one week, and the calculation uses UTC calendar days so daylight-saving changes never shift the answer by an hour.
Typical uses
- Contract and notice periods: 30, 60 or 90 days from a given start date.
- Return windows and warranty expiry dates.
- Pregnancy and project planning: counting forward in weeks from a known date.
- Subscription renewals and payment due dates.
- Looking back: what was the date 100 days ago?
Calendar days versus business days
This calculator counts every calendar day, including weekends and holidays. If a deadline is stated in working days, use the working days calculator on this site instead, which skips weekends and any holidays you list. Legal and contractual deadlines can have specific rules about how days are counted, for instance whether the start day is included, so check the wording of your agreement. The tool provides arithmetic and not legal advice.
Privacy
Dates never leave your browser. The start date defaults to today according to your device clock.