How to use the days between dates calculator
- Start Date and End Date: pick both dates, or press Use today. If the start is later, the tool swaps the two for you.
- Include the end date: tick it when both the first and the last day count, as with a hotel stay or a leave request.
- Read the headline in years, months and days, then the cards for total days, weeks, business days and hours. Results update as you type.
- Press Add or subtract days to find a date instead. Enter a Starting Date, a Number of Days, a Direction, and choose calendar or business days under Count.
How the calculation works
Each date becomes a day number on the Gregorian calendar, using Howard Hinnant's civil-date algorithms, so time zones and daylight saving never shift the answer. Total days is the difference between the two numbers. For years, months and days, the tool adds whole months to the start date, keeps the largest count that does not pass the end date, and reports the rest as days. When the start day does not exist in a month, such as January 31 plus one month, the month ends on its last day, so January 31 to March 1, 2026 reads 1 month and 1 day.
Business days are the Monday to Friday dates after the start date, up to and including the end date, which matches Excel's WORKDAY. With Include the end date ticked, both dates count, as in NETWORKDAYS.
Worked example
The page opens on Monday, March 17, 2025 and Tuesday, October 20, 2026. It shows 1 year, 7 months, 3 days: 582 total days, 83 weeks and 1 day, 416 business days, 166 weekend days, 13,968 hours and 19 whole months. Ticking Include the end date gives 583 days, 1 year, 7 months, 4 days and 417 business days. In the add mode, 30 calendar days after Thursday, January 1, 2026 is Saturday, January 31, 2026, and 30 business days after it is Thursday, February 12, 2026.
Limits and edge cases
- Dates run from October 15, 1582 to December 31, 9999. Countries adopted the Gregorian calendar at different times, so older dates may not match historical records.
- Public holidays are not removed from the business-day count, and only Saturday and Sunday are weekends. Subtract local holidays by hand.
- Times of day are ignored. Total hours is 24 per calendar day, so the 23-hour and 25-hour days around daylight saving changes are not modeled.
- The add mode takes whole numbers up to 3,000,000 and warns you when the result would fall outside the supported dates.
- For a live countdown use countdown to date, for an age in years, months and days use the age calculator, and for a due date try the pregnancy due date calculator.
Frequently asked questions
How many days are there between two dates?
Subtract the earlier date from the later one. From March 17, 2025 to October 20, 2026 that is 582 days. If you count both the first and the last day, tick Include the end date and the answer becomes 583.
How do I count business days between two dates?
The Business Days card counts Monday to Friday dates after the start date through the end date. The sample dates give 416. Public holidays are not removed, so subtract any that fall on a weekday in your range.
How do I find the date 90 days from a given day?
Open Add or subtract days, enter the Starting Date, type 90 as the Number of Days and leave Direction on Add days and Count on calendar days. From January 1, 2026 it returns Wednesday, April 1, 2026.
Why do two calculators give different months for the same dates?
Months have different lengths, so a span that starts on the 29th, 30th or 31st can be split in more than one reasonable way. This tool shortens the month when needed, so January 31 to March 1, 2026 reads 1 month, 1 day. The total day count never differs.