Date Calculator

Find the number of days between two dates. Enter the start and end year, month, and day.

Days Between
— days
Calendar days.

Usage Tip

Month is a number from 1 (January) to 12 (December). If the end date is before the start, the result still shows the size of the gap.

THE MATH
Days between = end date − start date
Weeks = days ÷ 7, approximate months = days ÷ 30.44
Date math counts calendar days, including any leap day in the span, so the day count is exact.
Months and years are approximate because their lengths vary.
Enter each date as year, month (1 to 12), and day.
Leap years add a day (Feb 29) and are handled automatically.
For age specifically, the age calculator gives exact years, months, and days.
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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.