About Date Calculator
Deadlines, notice periods, project schedules and visa windows all come down to counting days between two dates, and counting them by hand across month ends and leap years is where mistakes creep in. This calculator takes two dates and returns the calendar-day difference, the same figure in weeks and days, and optionally a Monday-to-Friday business-day count.
The second mode works the other way around: pick a starting date, add or subtract a number of days, weeks, months or years, and get the resulting date with its weekday. Months and years use calendar arithmetic, so 31 January plus one month lands on the last day of February rather than slipping into March. Everything runs locally from calendar dates.
What this tool does
Two date modes
Switch between measuring the gap between two dates and moving one date by an offset, without reloading the page.
Calendar-day difference
The exact number of days between the dates, plus the same duration written as weeks and days and an inclusive count.
Optional business days
Tick one box to count Monday-to-Friday working days and see the weekend days separately; public holidays are not assumed.
Add days, weeks, months or years
Choose the unit and direction, then read the resulting date, its weekday and the ISO form in one view.
Calendar-aware month arithmetic
Adding a month to 31 January gives the last valid day of February, the same clamping convention billing and payroll systems use.
Date-only local arithmetic
Dates are treated as plain calendar days with no timezone conversion, so a document dated 1 May stays 1 May anywhere in the world.
How to use Date Calculator
- 01
Choose a mode
Pick Date difference to measure the gap between two dates, or Add / subtract to move a date forwards or backwards.
- 02
Enter the dates
Use the date pickers or type the dates in year-month-day order; the start date defaults to today.
- 03
Count business days if needed
Tick the business-day option to exclude Saturdays and Sundays from the difference.
- 04
Read the result
The headline is the gap in calendar days, with weeks and days, business days and the inclusive count underneath.
- 05
Copy or reset
Copy the day count or ISO date, then press Reset to return both modes to today and start again.
How this tool works
- Works with
- Dates
- Processing
- Client-side, in your browser. Nothing is uploaded.
- Requirements
- Chrome, Edge, Firefox or Safari · JavaScript enabled
Limitations worth knowing
- The end date is excluded from the day count, so add one when both dates should count as days.
- Business days exclude weekends only; public holidays and company-specific non-working days are not modelled.
- Dates are limited to the years 1 to 9999, and offsets that would leave that range are rejected with an error.
Privacy and file handling
Dates and offsets are compared in your browser using local calendar arithmetic. Nothing is uploaded, stored or logged, and no request leaves your device while you calculate.
Read the full privacy policy