Count Days, Weeks, and Months Between Any Two Dates
Whether you are tracking a project deadline, planning a leave request, counting down to an event, or working out an invoice period, knowing the exact span between two dates saves guesswork. This calculator gives you the difference in every common unit — total days, full weeks plus remaining days, calendar months, and years — along with the number of business days that excludes weekends.
Date Difference Mode
Pick a start and end date and the calculator shows the span between them. The"include end date" checkbox adds one day to the count, which is useful when both the first and last day should be counted — rental periods, conference schedules, and medication courses often work this way. The result always shows a positive number regardless of which date comes first.
Add and Subtract Mode
Start from any date and add or subtract a specific number of days, weeks, months, or years to find the resulting date. This is how you answer questions like"what date is 90 days from today" or"what was the date 6 months ago." Adding months advances the month number while keeping the same day-of-month, clamping to the last valid day when needed — so January 31 plus one month lands on February 28 (or 29 in a leap year).
Business Days
The business-day count in the difference mode excludes Saturdays and Sundays, giving you the number of working days in a span. This is the number HR systems use for leave balances, the figure project managers use for effort estimates, and the count shipping companies use for delivery windows. Public holidays vary by country and are not excluded automatically — add them to the result manually if your scenario requires it.
Leap Years and Edge Cases
The calculator uses the browser's Date object, which correctly handles leap years, variable-length months, and century boundaries. February 29 appears only in leap years, and month arithmetic that would land on a nonexistent day (like adding one month to January 30) clamps to the last valid day of the target month rather than spilling into the next one.
Common Uses
Freelancers use date differences to calculate billing periods. Travelers count days between booking and departure to track cancellation windows. Developers test date logic by verifying their code matches this calculator's output. Students count days until exams or between semesters. In each case, the calculator replaces error-prone mental math with an instant, verifiable answer.
Privacy
All calculations run locally in your browser. No dates are sent to any server or stored anywhere.