Common Scenarios & Examples
Here are some specific questions this calculator answers instantly:
If you check on October 1st, there are exactly 85 days until December 25th.
How to use: Use the Holiday Shortcut to select "Next Christmas" for the End Date.
Born on Jan 1, 1990? By Jan 1, 2024, you have lived exactly 12,418 days.
How to use: Enter your full Date of Birth as the Start Date and set the End Date to "Today".
A project running from Jan 15th to March 31st (leap year) spans exactly 76 days.
How to use: Enter project start/end dates. Check "Include End Date" if the deadline day counts as work.
Left the US on May 1st and returned Sept 1st? Useful for the IRS Physical Presence Test.
How to use: Enter your Departure Date as Start and Return Date as End.
Pro Tip: Travel days don't count as "Foreign Days". Subtract 1 from the result to get the strict count.
Getting married on June 15th? Find out exactly how many days you have left to plan.
How to use: Click the "Today" button for Start Date, then enter your Wedding Date as the End Date.
How the Days Between Calculator Works
Calculating the duration between two dates is more than just counting numbers on a calendar. It involves accounting for the varying lengths of months (28, 30, or 31 days) and the extra day in Leap Years.
This tool uses the standard Gregorian calendar to ensure accuracy. It calculates the difference in milliseconds between the two timestamps and converts that into full 24-hour days.
Including the End Date
A common source of confusion in date math is the "Fence Post Error."
- Standard (Exclude End Date): If you start on Monday and end on Tuesday, the duration is 1 day. This is the default setting.
- Inclusive (Include End Date): If you are booking a hotel or taking leave, Monday to Tuesday might be considered 2 days of occupancy. Check the "Include End Date" box to add +1 to your count.
Frequently Asked Questions
How many weeks are in 100 days?
100 days is exactly 14 weeks and 2 days. You can use this calculator to check any number of days.
Does this account for Leap Years?
Yes. If your date range includes a February 29th (like in 2024 or 2028), the total day count will automatically include that extra day.
How do I calculate "Business Days" only?
This tool calculates total calendar days (including weekends). If you need to exclude Saturdays and Sundays for work deadlines, please use our Business Days Calculator.