Date Calculator
Calculate the difference between two dates, or add and subtract days from a starting date. All calculation happens in your browser.
Both dates are the same — the difference is 0 days.
Calculated locally in your browser.
Two modes
- Date Difference — enter a start date and end date to see the gap in years, months, days, and total days.
- Add / Subtract Days — enter a starting date and a number of days to find the resulting date.
Examples
- Date difference: January 1, 2024 → September 18, 2026 = 2 years, 8 months, 17 days (990 total days)
- Add days: January 1, 2026 + 30 days = January 31, 2026
- Subtract days: March 1, 2024 − 1 day = February 29, 2024 (leap year handled correctly)
Accuracy notes
- Leap years and different month lengths are accounted for in all calculations.
- All dates are calculated in your browser's local timezone using local midnight — no timezone offset issues.
- When the end date is before the start date in Difference mode, the calculator reports the absolute difference and indicates the order.
FAQ
- How are months counted? Calendar months — from the 1st of one month to the 1st of the next is exactly 1 month, regardless of how many days it contains.
- What happens when adding days across months/years? The calculator correctly rolls over month and year boundaries.
- Is my data sent anywhere? No — all calculations happen locally in your browser.