Date Difference Calculator
Calculate the exact number of days, weeks, months, and years between any two dates. Supports inclusive and exclusive date counting. Useful for project timelines, contract periods, lease durations, and countdown planning.
Formulas, assumptions, and rounding are documented in our calculator methodology.
Uses for Date Difference Calculations
Project planning: calculate how many working days remain before a deadline. Contracts and leases: verify that a 12-month lease from March 1 ends on February 28 (or 29 in a leap year). Loan terms: confirm the exact number of months in a financing agreement. Employment: calculate probation period end dates or benefit eligibility dates. Pregnancy: count weeks of gestation from the last menstrual period. Travel: verify visa validity days remaining. Anniversaries and events: find how many days until or since any date.
Inclusive vs. Exclusive Counting: Which to Use
Exclusive counting (default): counts days strictly between the two dates. Use this for 'how many days until' or 'how many days elapsed between' questions. Inclusive counting: counts both the start and end day. Use this for event durations (a conference that runs Monday through Friday is 5 days inclusive), periods where both endpoints are full days, and legal documents that say 'from [date] to [date], inclusive.'
Frequently Asked Questions
- Exclusive counting (the default) counts only the days between the two dates, not including the start or end day itself. Inclusive counting adds 1 to include both endpoints. Example: from Monday to Friday — exclusive = 4 days; inclusive = 5 days. For event durations where both the start and end day are full days, use inclusive counting.
- Yes. The calculator correctly counts every day including leap days (February 29 in leap years), so the day count is accurate regardless of how many leap years fall within the date range.
- This calculator counts actual calendar days — not an assumed 365 or 360 days per year. If the range spans a leap year, that year contributes 366 days. This gives the most accurate possible result for any date range.
- The calculator computes complete months elapsed between the two dates, then shows remaining days beyond the last complete month. This matches how 'months between dates' is typically understood — the same logic used to calculate loan terms and lease durations.