Date Difference Calculator
Find how many days, weeks, months and weekdays are between any two dates, with an option to count the end date as well.
🔒 Runs entirely in your browser. Nothing you enter is sent to a server.
How many days until a holiday, a deadline or a due date? How long ago did a project start? This date difference calculator counts the days between any two dates and also expresses the gap in years, months and days, in weeks and in weekdays.
How to use the date difference calculator
- Pick the start date.
- Pick the end date.
- Choose whether to include the end date in the count.
The results show the total days, the same span as years, months and days, as weeks and days, the number of weekdays (Monday to Friday) and the total in hours.
How the difference is calculated
The total number of days is the end date minus the start date. The calculator works on calendar dates, so daylight saving changes and time zones never add or remove a day.
Days = end date − start date
Days (including end date) = end date − start date + 1
Weeks = Days ÷ 7, remainder shown as days
Hours = Days × 24For the years, months and days version, it counts whole calendar months from the start date first, then the days left over. When a start date falls on a day that a shorter month does not have, such as the 31st, the last day of that month is used.
Weekdays are counted by taking five for every full week in the range and then checking the remaining days one by one.
Worked example
From Monday 2 March 2026 to Friday 25 December 2026, without the end date:
- Total: 298 days
- Whole months: 2 March to 2 December is 9 months, and 2 December to 25 December is 23 days, so 9 months, 23 days
- 298 ÷ 7 = 42 weeks and 4 days
- Weekdays: 42 full weeks give 210, and the remaining 4 days (Monday to Thursday) add 4, so 214 weekdays
With “include the end date” turned on, the total becomes 299 days and Friday 25 December adds one more weekday, giving 215.
Including or excluding the end date
This choice is the most common source of off-by-one mistakes:
| Situation | Include end date? |
|---|---|
| Days until an event or deadline | No |
| How long ago something happened | No |
| Length of a holiday, first day to last day | Yes |
| Number of days in a contract period | Usually yes, check the wording |
| Nights in a hotel | No |
| Days you are at a hotel, arrival to departure | Yes |
A good test: from Monday to Tuesday is 1 day without the end date, and 2 days with it.
Practical uses
- Deadlines and countdowns. See exactly how many days, or working days, you have left.
- Notice periods and contracts. Check that a 30-day or 90-day period ends when you think it does.
- Pregnancy and baby milestones. Count weeks and days from a known date.
- Travel. Check the length of a trip against visa limits such as 90 days in a 180-day window.
- Billing. Work out how many days of a month a service was used for pro-rated charges.
Tips and pitfalls
- Public holidays are not excluded. The weekday count is Monday to Friday only. Subtract holidays in your region for an exact working-day figure.
- Legal deadlines have their own rules. Courts and authorities often say whether the first day counts and what happens when a deadline falls on a weekend. Check the rule that applies to you.
- Very long spans are fine. You can count across centuries, and every leap day is included.
All calculations run in your browser, and the dates you enter are not stored.
Frequently asked questions
Should I include the end date?
It depends on what you are counting. For the gap between two dates, such as days until a deadline, leave it off. For a span where both days count, such as a hotel stay from check-in to check-out day or a holiday from the first to the last day off, turn it on. Including it adds one day.
How are weekdays counted?
Weekdays are Monday to Friday between the two dates, using the same include-end-date setting. Public holidays are not removed, because they differ by country and region. Subtract any holidays that fall in your range to get working days.
Does the calculator handle leap years?
Yes. Every 29 February that falls between the two dates is counted, so a span across a leap year automatically has the extra day.
What happens if the end date is before the start date?
The calculator swaps them, works out the difference and shows the total days with a minus sign, so you can see the end date comes first.
Why is the number of months sometimes surprising?
Months have different lengths, so the same number of days can be a different number of months depending on where you start. The calculator counts whole calendar months from the start date and then the remaining days.