What this calculator does
Find out exactly how many days there are between any two dates. The count allows for months of different lengths and for leap years. How long does a trip last? How many days does a lease or contract cover? How much time has passed since an event? Each of these is a question about that gap.
Along with the total days, you get the span in several other forms. It shows whole weeks, decimal weeks, complete months, and years, months and days. It also shows hours and minutes, and splits the days into weekdays and weekend days.
Where it's used
Why this math matters outside the classroom:
- Days between dates. From January 1 to December 31 of 2026 there are 364 days, or 365 counting both ends.
- Lease and contract terms. Tenants count the months and days between a move-in date and a lease end date.
- History projects. Students work out how long ago an event took place in years, months and days.
- Pet milestones. Owners count the weeks since an animal was adopted to mark milestones such as its first year at home.
How to use it
- Enter a start date and an end date. They start out as today and 30 days from today.
- Tick “Include the end date” if both the first and last day should count. You'd do this when counting the days of a stay or an event.
- Read the total and the breakdowns. If the end date is earlier than the start date, the two are swapped for you, and the summary says so.
- For working days with public holidays taken off, switch to the business days calculator.
What the inputs mean
- Start date
- The first date of the span.
- End date
- The last date of the span. It can be earlier than the start. The dates are swapped, so the result is always a positive count.
- Include the end date (count both the first and last day)
- With this off, you get the days from the start to the end: Monday to Wednesday is 2 days. With it on, both ends count: Monday to Wednesday is 3 days. Turning it on adds one day to the total.
Formula and method
total days = end date − start date total days = end date − start date + 1 (end date included) weeks = total days ÷ 7 (whole part), leftover days = the remainder weekend days = total days − weekdays hours = total days × 24; minutes = hours × 60
The calculator gives each date a day number, counting along the Gregorian calendar (the one most of the world uses). Then it subtracts the two numbers. That way, leap days are counted automatically. Including the end date is the same as measuring up to the day after it.
Weekdays are Monday through Friday. Every full week adds five. The leftover days are checked one at a time. Public holidays aren't removed, because they differ by country, region and employer.
The years, months and days figure counts complete calendar months first, then the days left over. Sometimes a monthly date doesn't exist, such as the 31st in a 30-day month. Then the calculator uses the last day of that month instead.
Worked example
A project runs from Monday, October 19, 2026 to Monday, November 2, 2026, without counting the end date.
- October 19 to November 2 is 14 days: 12 left in October after the 19th, plus 2 in November.
- 14 ÷ 7 = 2 weeks with 0 days left over.
- Two full weeks contain 2 × 5 = 10 weekdays, leaving 4 weekend days.
- No complete month fits, since that would need October 19 to November 19. So the calendar figure is 0 years, 0 months, 14 days.
- Hours: 14 × 24 = 336 hours, or 20,160 minutes.
Result: The span is 14 days: 2 weeks, of which 10 are weekdays and 4 are weekend days. That's 336 hours. With the end date included, it would be 15 days and 11 weekdays.
Understanding the result
Whether to include the end date depends on your question. “How many days until the 25th?” leaves it out. “How many days is the festival, the 23rd to the 25th?” includes it.
The weekday count is the most business days there could be. Subtract any public holidays and days off in the span to get your working days.
Assumptions and limitations
- Both dates are on the Gregorian calendar. They're treated as whole days, whatever the time zone.
- Weekdays are Monday to Friday. Saturday and Sunday are the weekend.
- Hours and minutes assume every day has 24 hours.
- Public holidays aren't taken out of the weekday count.
- It doesn't handle times of day. Use the time duration calculator for hours and minutes.
- Workweeks that don't run Monday to Friday aren't supported.
- On the days clocks change for daylight saving time, a real day has 23 or 25 hours. The hours figure ignores that.
Frequently asked questions
Should I include the end date?
Include it when you're counting days on which something happens, such as the days of a hotel stay or a leave of absence. Leave it out when you're measuring the time until a date, such as a countdown to a deadline.
How many days are there between two dates in different years?
The same method works across years. Each date becomes a day number, and the two are subtracted, so every leap day in between is counted. For example, January 1, 2025 to January 1, 2026 is 365 days. But January 1, 2024 to January 1, 2025 is 366, because 2024 had a February 29.
How many months are between two dates?
Read Complete months. It counts how many times you can step forward one calendar month from the start without passing the end. So January 15 to April 20 is 3 complete months plus 5 days. Months differ in length, so a decimal month count would depend on which months were involved. That's why it isn't shown.
Are public holidays excluded from weekdays?
No. The weekday figure counts every Monday to Friday in the span. Holidays vary by place and employer, so subtract the ones that apply to you. Or use the business days calculator, which lets you take them off.
What happens if I enter the dates in the wrong order?
They're swapped for you, so you always get a positive number of days. The summary line notes that the swap happened.
Why is January 31 to March 1 shown as 1 month and 1 day?
There's no February 31, so one month after January 31 is moved back to the last day of February. From there, it's one more day to March 1. In a leap year the same span is also 1 month and 1 day, counted from February 29.
How this calculator is checked
Method: Gregorian day-number subtraction; calendar-month counting with end-of-month clamping; Monday–Friday weekday count. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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