Days Between Dates Calculator - Calculate Duration
Calculate the exact number of days, weeks, months, and years between two dates. Find the duration instantly with our accessible, mobile-first date calculator.
Date Selection
Enabling this option adds one day to the duration so that the final day is counted as part of the period.
How to Use This Calculator
Enter both the start and end dates to see the precise span between them. Check the "Include the end date" box if you want the final day to count toward the total. When everything is filled in, hit Calculate to update the results instantly.
- Total days round any daylight savings or timezone transitions by comparing midnight-to-midnight values.
- Weeks are computed by dividing the rounded day total by seven, and months use the average length of a Gregorian month (365.2425 / 12).
- The summary breaks the span into years, months, and days so you can understand the precise calendar difference.
Methodology
Why this calculator helps
- Instantly see duration in total days, weeks, and approximate months.
- Get a clear "Years, Months, Days" summary for intuitive understanding.
- Automatically includes leap years and handles calendar month lengths correctly.
- Option to include the end date for inclusive counting.
- Fully accessible (WCAG AA) and mobile-first layout.
Related Time & Date Tools
Full original guide (expanded)
The legacy page included a detailed audit spine that documented the raw formulas, variable definitions, sources, and changelog entries found below. We preserved every item there so that no reference material is lost during the refactor.