How many days between two dates including both end dates?

This calculator gives the exclusive difference (End − Start). To include both end dates, add 1 to the result.

Does the calculator account for leap years?

Yes. The calculation converts both dates to a day count that automatically handles the extra day in leap years (e.g., February 29).

What is the maximum date range I can calculate?

The calculator supports years from 1900 to 2100, covering any practical business, legal, or historical date difference.

Mathematics

Date Difference Calculator

Enter two dates and this calculator returns the exact difference in days, weeks, approximate months, and approximate years. Useful for project deadlines, contract durations, age comparisons, and historical date research.

Formula

Difference = End Date − Start Date (in days)

Both dates are converted to their Julian Day Number (a standard astronomical day count). The difference gives exact days. Weeks = days ÷ 7. Approximate months = days ÷ 30.4375. Approximate years = days ÷ 365.25. Leap years are handled automatically by the calendar conversion.

Worked example

How many days are between January 1, 2024 and March 23, 2026?

1.From: January 1, 2024
2.To: March 23, 2026
3.2024 is a leap year (366 days)
4.Days remaining in 2024 from Jan 1: 366 days
5.Days in 2025: 365 days
6.Days in 2026 through March 23: 31 (Jan) + 28 (Feb) + 23 (Mar) = 82 days
7.Total: 366 + 365 + 82 = 813 days

813 days = 116.14 weeks ≈ 26.7 months ≈ 2.23 years.

Assumptions and limitations

Uses the proleptic Gregorian calendar for all dates.
Leap years follow the standard rule: divisible by 4, except centuries unless also divisible by 400.
Months and years are approximate (based on average month = 30.4375 days, year = 365.25 days).
Results are the same regardless of time zone since only calendar dates are used.