How to use the date calculator
Add or subtract: pick a start date, choose add or subtract, and enter any combination of years, months, weeks and days. The result updates as you type.
Days between dates: pick a start and end date to see the number of days between them, plus the same span in weeks, months, weekdays and hours. Tick "include the end date" if both the first and last day should count — for example, a hotel stay or event that runs from the 1st to the 5th inclusive is 5 days, not 4.
How months are added
Adding a month keeps the same day number where possible: March 15 + 1 month = April 15. When that day doesn't exist in the target month, the calculator uses the last day of that month, so January 31 + 1 month = February 28 (or 29 in a leap year). Years and months are applied first, then weeks and days.
Business days
The "Weekdays (Mon–Fri)" figure counts Monday through Friday only. It does not remove public holidays, which differ by country and employer — subtract those yourself if your deadline is in working days.
Examples
- Payment due net 30 from an invoice dated today → add 30 days.
- Project kickoff to launch → use "days between dates" and read the weekdays figure.
- Six-month review → add 6 months to the start date.