Days Between Dates Calculator
Calculate the exact number of days, weeks, months, and years between any two dates. Includes business days and weekend counts. See also Date Calculator and Work Days Calculator.
How to Calculate Days Between Two Dates
The days between dates calculator finds the exact number of calendar days separating two dates. It computes the absolute difference in milliseconds, then converts to days. The "include end date" option adds one day to the count, which is useful when both the start and end dates should be counted (e.g., rental periods, event durations). Business days exclude Saturdays and Sundays from the count.
Calculation Formulas
Total Days = |end_date - start_date| / 86,400,000 ms
Inclusive Count = Total Days + 1
Weeks = floor(Total Days / 7)
Business Days = Total Days - Weekend Days
Total Hours = Total Days x 24
Total Minutes = Total Days x 1,440
Leap Year Considerations
When calculating days between dates that span February, leap years add an extra day. A year is a leap year if it is divisible by 4, except for century years which must be divisible by 400. This means 2024 is a leap year, 2100 is not, and 2000 was. The calculator handles this automatically using JavaScript Date objects which account for the Gregorian calendar rules.
Common Date Intervals Reference
| Period | Calendar Days | Business Days | Weekends |
|---|---|---|---|
| 1 Week | 7 | 5 | 2 |
| 2 Weeks | 14 | 10 | 4 |
| 1 Month (30d) | 30 | ~22 | ~8 |
| 1 Quarter (90d) | 90 | ~64 | ~26 |
| 6 Months (182d) | 182 | ~130 | ~52 |
| 1 Year (365d) | 365 | ~261 | ~104 |
| 1 Year (366d, leap) | 366 | ~262 | ~104 |
Frequently Asked Questions
Should I include the end date in the count?
It depends on your use case. For "how many days until" questions, exclude the end date. For rental periods or event durations where both start and end days count, include it. For example, a hotel stay from Jan 1 to Jan 3 is 2 nights but 3 days (inclusive).
How are business days calculated?
Business days count only Monday through Friday, excluding Saturdays and Sundays. This calculator does not account for public holidays. For holiday-aware calculations, use the Work Days Calculator.
Does this account for leap years?
Yes. The calculator uses actual calendar dates, so February 29 in leap years is counted correctly. A span from Jan 1 to Dec 31 in a leap year is 365 days (or 366 inclusive).
Can I enter the end date before the start date?
Yes. The calculator uses the absolute difference, so the order does not matter. It will always show a positive number of days.
How do I calculate months between dates?
The calculator shows the result in multiple formats including months + days and years + months + days. It counts complete calendar months (not fixed 30-day periods) for accuracy.
What is the difference between calendar days and working days?
Calendar days include every day (Monday through Sunday). Working days (business days) exclude weekends. In a typical week, there are 7 calendar days but only 5 working days.