Add or subtract days, weeks, months, and years from any date — or find the difference between two dates.
The Date Calculator makes everyday date math effortless. Add or subtract days, weeks, months, and years from a starting date to find a future or past date, or measure the exact gap between two dates. It correctly handles leap years and the different lengths of months, so your results are always accurate — no manual counting on a calendar.
The tool works in two modes. In add/subtract mode, you pick a start date and enter an amount to move forward or backward — useful for forecasting deadlines and expiry dates. In difference mode, you pick two dates and get the interval between them in days, weeks, months, or years. Both modes account for calendar quirks like February 29th and 30- versus 31-day months.
Counting days on a calendar looks simple until the details bite. Months have 28, 30, or 31 days; leap years add a February 29th every four years (with century exceptions); and spans that cross a year boundary are easy to miscount. Add the fact that people naturally lose track after a few weeks, and manual date arithmetic becomes a reliable source of small but costly mistakes — a missed deadline, an early expiry, a misdated invoice. A calculator removes that risk by applying the calendar rules perfectly every time.
Find the date 90 days after a project kickoff:
2026-01-1590 days2026-04-15The calculator counts through January, February (28 days in 2026), March, and into April to land on the exact date — something that is easy to miscount by hand.
Decide up front whether your count should include or exclude the start date — a "30-day" period can mean different end dates depending on that choice, and being consistent avoids off-by-one errors. When adding months rather than days, remember that month arithmetic can land on a shorter month: adding one month to January 31st has no February 31st to reach, so calculators roll to the month's end. For legal or contractual deadlines, double-check whether weekends and holidays should be excluded, and use the difference mode to confirm the interval matches your intent.
Yes — it accounts for varying month lengths and leap years when adding or subtracting.
Yes — enter a start and end date to get the exact interval.
Yes. February 29th and leap-year lengths are handled automatically.
Yes — enter a negative or subtract amount to move backward in time.
Decide on a convention and apply it consistently; the difference mode helps you confirm the exact interval.
Yes. All calculations run locally in your browser.
Explore Tooloogle's other date and time utilities, and the Factorial Calculator for quick math.
How to Use Date Calculator — Add or Subtract Days
Choose the date you want to calculate from.
Enter the days, weeks, months, or years to add or subtract.
The resulting date or difference updates instantly.
Add or subtract days, weeks, months, and years from any date — or find the difference between two dates.
Tool Use:
1Added:
Sep 11, 2026Type:
Free ToolPrivacy:
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