Days Between Dates Calculator: Accurate Date Calculator
Easily calculate the exact number of days between any two dates with our free online calculator. Accounts for leap years.
Enter Your Dates
Result
30 days
This is equivalent to 4 weeks and 2 days.
How Our Calculator Works
Instead of counting one day at a time, our calculator uses a highly efficient mathematical formula called the **Rata Die method**. This professional standard, used in software systems worldwide, converts each date into a unique "day number" representing the total days passed since a fixed point in history (January 1, AD 1). By subtracting these two numbers, it finds the difference instantly and accurately.
Start Date
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Day Number 1
End Date
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Day Number 2
Total Days
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Difference
The Challenge of Counting Days
The Problem with Leap Years
The Gregorian leap year rule is complex: a leap day occurs every 4 years, *except* for years divisible by 100, *unless* they are also divisible by 400. This means 2000 was a leap year, but 1900 was not. Our calculator handles this logic perfectly.
A Tale of Ten Missing Days
In 1582, to correct the calendar's drift, Pope Gregory XIII ordered a jump from October 4 to October 15. Our tool uses the standard **proleptic Gregorian calendar**, applying modern rules consistently to all dates to avoid historical ambiguity.