Date Calculator
Calculate days between dates, add or subtract days, and count business days.
About This Tool
The Date Calculator computes the difference between two dates in years, months, and days, and can add or subtract a specified number of days from any date. It also supports business day calculations that exclude weekends and public holidays, making it ideal for project planning, contract management, and deadline tracking.
How to Use
- Choose a mode: Date Difference, Add/Subtract Days, or Business Days.
- For Date Difference: enter two dates to find the number of days between them.
- For Add/Subtract: enter a base date and number of days to add or subtract.
- For Business Days: enter two dates to count only weekdays (Mon-Fri).
- Results update instantly when you click Calculate.
Frequently Asked Questions
What is the difference between calendar days and business days?
Calendar days include all days (weekdays + weekends). Business days only count Monday through Friday, excluding weekends. For example, 1 calendar week = 7 calendar days but only 5 business days.
Does this calculator account for holidays?
This calculator counts business days by excluding weekends (Saturday and Sunday) only. Public holidays are not excluded as they vary by country and year. For precise business day counts, manually subtract applicable holidays.
How do I calculate a deadline?
Use the Add/Subtract mode. Enter your starting date and the number of days in your deadline. The calculator will show the exact date. For business-day deadlines, use the Business Days mode to find when a certain number of working days will pass.
Does this work with leap years?
Yes, this calculator correctly handles leap years. February 29th is properly accounted for in all calculations.
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How It Works
Date difference calculation breaks down the interval between two dates into years, months, and remaining days using the Gregorian calendar. The algorithm accounts for varying month lengths (28–31 days) and leap years (divisible by 4, except centuries not divisible by 400).
For date addition/subtraction, the calculator adds or subtracts the specified number of calendar days to the start date. Leap year handling ensures February 29 is correctly processed: a year is a leap year if divisible by 4, unless divisible by 100, unless also divisible by 400.
Business day calculations iterate through each day in the range, counting only Monday through Friday while skipping weekends. When holidays are included, the calculator checks each date against a holiday list for the selected country/region. The result shows both the total calendar days and the net business days between two dates.
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