Date Calculator: Days Between Two Dates
The Date Calculator determines the precise calendar duration between two dates. Whether calculating contract durations, project milestones, notice periods, or age milestones, it accounts for varying month lengths (28, 29, 30, or 31 days) and leap years under the Gregorian calendar standard (ISO 8601).
Select Dates
Includes automatic leap year adjustments under ISO 8601 calendar calculation standards.
Calendar Span Formula
- Days Difference = Epoch timestamp of Date 2 minus Epoch timestamp of Date 1 divided by 86,400,000 milliseconds.
- Weeks = Floor(Total Days / 7) with remaining days as modulus.
- Business Days = Total calendar days excluding Saturdays and Sundays.
Practical Worked Example
Calculating the project duration between March 15, 2026 and October 31, 2026.
- March remaining days: 31 - 15 = 16 days.
- Full intermediate months (April through September): 30 + 31 + 30 + 31 + 31 + 30 = 183 days.
- October elapsed days: 31 days.
- Total duration: 16 + 183 + 31 = 230 calendar days (32 weeks and 6 days, or 7 months and 16 days).
Frequently Asked Questions
Are both the start date and end date counted in the calculation?
By standard convention, the start date is counted as day zero (Day 1 begins after 24 hours). If your contract specifies inclusive counting (both start and end dates included), add 1 additional day to the calculated result.
How does the calculator handle leap years?
The engine applies the standard Gregorian rule: leap years occur in years evenly divisible by 4, except for century years unless they are also divisible by 400. February 29 is automatically counted when the interval spans a leap year.
Can I calculate business days excluding public holidays?
The core business days output automatically excludes weekend Saturdays and Sundays. For official government holidays, deduct the regional public holidays observed in your state or country from the business day count.
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Disclaimer: This tool provides computational estimates for educational and informational purposes only. It does not constitute personal financial, tax, or legal advice. Consult a certified financial planner or CA for specific advice.