How to use the Date Calculator
- Pick a start date (or leave it for today).
- Choose add or subtract and the amount and unit.
- Read the resulting date and weekday.
Days, business days and months
Business days skip Saturdays and Sundays (public holidays vary by country and are not removed). Adding months keeps the day of the month when possible; January 31 + 1 month becomes the last day of February. To count the days between two dates, use the Date Difference Calculator.
Also searched as: add days to date, subtract days from date, days from today, business days calculator, what date is 90 days from today.
Tools that pair well with the Date Calculator
- Age Calculator — Enter a date of birth to get the exact age in years, months and days — plus total days and weeks lived, the weekday you were born on, a countdown to the next birthday and your star sign.
- Countdown Timer — Set a countdown in seconds — type hours, minutes and seconds or tap a preset — and get an alarm sound and an optional notification when it reaches zero.
- Time Duration Calculator — Find the time between two clock times (even past midnight), or add up durations like 1:45 + 2:30 — in hours and minutes and decimal hours.
- Due Date Calculator — Estimate your due date from the first day of your last period, your conception date or an IVF transfer — and see how many weeks pregnant you are, your trimester and the key dates ahead.
Frequently asked questions
What date is 90 days from today?
Leave the start date empty, choose Add, 90 and Days.
Are public holidays excluded from business days?
No — only weekends are skipped, because holidays differ between countries.
Is anything I enter saved or sent?
No. The calculation runs in your browser. Your last inputs are remembered on this device only, so the page opens where you left off.
Can I install Date Calculator as a web app and use it offline?
Yes. Date Calculator is an installable web app (PWA) — installed from your browser, not downloaded from an app store. Click Install app at the top of this page in Chrome or Edge (Windows, macOS, Linux, ChromeOS) or on Android, use Share → Add to Home Screen on iPhone and iPad, or File → Add to Dock in Safari 17+ on a Mac. It then opens in its own window with its own icon, and because it runs entirely in your browser it keeps working offline. Firefox on desktop can’t install web apps. How installing works.