Date Difference Calculator - Days Between Dates Calculator Free

How to Use the Date Difference Calculator

1. Select the start date — click the date picker and choose your starting date (e.g., project kickoff, birth date, or contract start)
2. Select the end date — choose the target or end date for your calculation
3. View the results — the calculator instantly shows total days, months, years, business days, weekend days, and weeks with remainder
4. Toggle business days — switch between calendar days and business days (Mon-Fri) to plan around work schedules
5. Reverse dates — swap start and end to quickly check the other direction

Perfect for project planning, contract duration, countdowns to events, and calculating age or tenure.

Features

• Total duration — years, months, and days between the two dates
• Business days count — number of weekdays (Monday-Friday) excluding weekends
• Weekend days count — total Saturdays and Sundays in the range
• Weeks + remainder — clean breakdown in full weeks and extra days
• Instant results — updates as you change either date
• Date picker — friendly calendar interface for date selection
• Simple summary view — at-a-glance difference at the top

Use Cases

• Project planning — calculate how many business days you have between project kickoff and the delivery deadline
• Contract duration — determine the exact length of a 90-day trial period or 12-month lease
• Age calculation — find the exact age in years, months, and days between a birth date and today
• Vacation planning — count total days including weekends for a holiday, or business days if requesting time off
• Billing periods — calculate the number of days between two invoice dates for daily-rate billing or interest calculations

FAQ

Does the calculator include both the start and end dates?

By default, it calculates the full period between two dates excluding the end date. For same-day calculations this shows 0 days. To include both dates, simply add 1 to the total.

How are business days defined?

Business days are Monday through Friday, excluding Saturday and Sunday. Holidays are not excluded — the calculator doesn’t account for public holidays, so subtract those manually if needed for your region.

Can I calculate age with this tool?

Yes — enter a birth date as the start date and today’s date (or any future date) as the end date. The calculator will show the exact years, months, and days, which is the standard age format.

What’s the maximum date range supported?

The calculator works with dates between January 1, 1900 and December 31, 2099. For historical dates outside this range, the results may not be accurate due to calendar system changes.

Does it account for leap years?

Yes — the calculator properly accounts for February 29th in leap years (years divisible by 4, except centuries not divisible by 400). The date picker also allows selecting February 29 on leap years only.