Count dates using calendar days rather than local-clock elapsed hours. The start date is included in work-day enumeration and the end is excluded unless the inclusive option is checked.
Check the stated input format, calculation convention and limits before using the result.
Check the example inputs, then calculate. Your values stay in this browser.
End must be on or after start; an equal pair yields zero unless the end is included.
Days Between Dates Calculator validates start date, end date, include the end date before applying the displayed equation. End must be on or after start; an equal pair yields zero unless the end is included.
Days Between Dates Calculator: days = (UTC(end) − UTC(start)) / 86400000 + inclusiveEnd. Input definitions: start = Start date; end = End date; inclusive = Include the end date. Use the selected convention throughout the calculation.
Days Between Dates Calculator baseline input: Start date: 2026-01-01; End date: 2026-01-31; Include the end date: not selected. Output: Calendar days = 30 days. Substitute these values into the displayed equation to reproduce the result.
Content and calculation reviewed:
Understand the calculation
Calendar-day subtraction excludes the end date by default. From February 28 to March 1 in leap year 2024 there are two day transitions: February 29 and March 1. Including the end adds one, producing three counted calendar dates. This is date arithmetic at UTC midnight, not a measure of local elapsed hours across daylight-saving changes.
days = (UTC(end) − UTC(start)) / 86400000 + inclusiveEnd
The detailed guide adds variable definitions, a reproducible example, a practice question and model limitations.
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