UtilibyWritten by the Utiliby editorial team · Last updated October 17, 2026 · Rules and formulas reviewed October 2026
What this free days between dates calculator does
How many days until a deadline, since a milestone, or between two events? A days between dates calculator answers in a second without counting on a calendar. This free online tool gives the exact number of days between any two dates, and the same span as weeks and days, years, months and days, hours, minutes and seconds. It also counts weekdays and weekend days and shows the day of the year and ISO week number for both dates.
A timeline draws the span with month marks and a marker for today. The second tab adds or subtracts years, months, weeks, days or working days from a date and tells you the weekday of the result. The third tab is a countdown to any event, with a table of the next dates for common holidays. All the maths uses real calendar days, including leap years, and runs in your browser.
How to use the days between dates calculator
- Pick the start and end dates. The result appears instantly.
- Choose whether to include the end date. Leave it unticked to count the gap, or tick it to count both days.
- Read the breakdown in days, weeks, months, hours and weekdays.
- Use the add or subtract tab to find a date a set time before or after another.
- Use the countdown tab for an event name and a live count of days left.
How the number of days is calculated
Every calendar date is converted to a serial day number, and the days between two dates are simply the difference of those numbers. This avoids the pitfalls of months of unequal length and leap years. From 17 October 2026 to 25 December 2026 the difference is 69 days. Counting both the first and last day gives 70. As calendar units, the same span is 2 months and 8 days, found by stepping forward whole months from the start date and counting the leftover days.
| From | To | Days |
|---|---|---|
| 17 Oct 2026 | 25 Dec 2026 | 69 |
| 17 Oct 2026 | 1 Jan 2027 | 76 |
| 1 Jan 2026 | 31 Dec 2026 | 364 |
| 1 Jan 2000 | 1 Jan 2026 | 9,497 |
| 20 Jul 1969 | 20 Jul 2026 | 20,819 |
Leap years and month lengths
A year has 365 days, except leap years, which have 366 because February gains a 29th day. A year is a leap year when it is divisible by 4, unless it is a century year, which must also be divisible by 400. So 2000 and 2024 were leap years, while 1900 and 2100 are not. The calculator uses true calendar arithmetic, so 1 February to 1 March is 29 days in 2024 and 28 days in 2023. When you add months, a day that does not exist in the target month is moved to the last day of that month, so 31 January plus one month is 28 February in a common year.
Inclusive and exclusive counting
Whether to count the end date depends on the question. For the gap between two dates, such as the age of a document or the days until an event, the standard method does not count the end date. For things where both days count, such as the length of a trip, a course or a rental period, you include the end date and add one. A trip from 1 to 7 June is six days apart but seven days long if you include both. The checkbox switches between the two, and the label above the result states which is in use.
Weekdays, weekends and working days
The tool counts Monday to Friday as weekdays and Saturday and Sunday as weekend days. From 17 October to 25 December 2026 there are 50 weekdays and 19 weekend days. Public holidays are not removed because they depend on country, region and employer. For payroll, delivery estimates or contract deadlines, use a dedicated working days calculator and check your holiday calendar.
Adding and subtracting days, weeks and months
The second tab finds the date a set time before or after a start date. Adding 100 days to 17 October 2026 gives Monday 25 January 2027, and subtracting 90 days gives 19 July 2026. You can combine years, months, weeks and days in one step, or add a number of working days that skips weekends. This is handy for due dates, notice periods, warranty ends, 30, 60 and 90 day plans, and project schedules.
Day of the year and ISO week numbers
The day of the year numbers days from 1 January as day 1, so 17 October 2026 is day 290. The ISO week number follows ISO 8601, in which weeks run Monday to Sunday and week 1 is the week with the first Thursday of the year. Some years have 53 ISO weeks. For example 1 January 2027 falls in week 53 of 2026. Week numbers are widely used in business planning, logistics and school calendars outside the United States.
Common uses
- Countdowns to holidays, weddings, exams or launch days.
- Project planning and deadlines.
- Legal and notice periods such as 14, 30 or 90 days (always confirm the rules).
- Pregnancy, travel and visa stays where days matter.
- Anniversaries and milestones, including 100 days together.
- Tracking habits and streaks.
Accuracy, privacy and responsible use
The calculator counts whole calendar dates in the Gregorian calendar, so time zones and daylight saving time do not affect results. Dates before the Gregorian calendar was adopted in different countries are not adjusted. Working-day counts ignore public holidays. For legal, immigration or financial deadlines, check the counting rules that apply. Nothing you enter is sent anywhere.
Related free tools
Use these free online tools together with this one:
- Find an exact age in years, months and days with the age calculator.
- Remove public holidays from a business-day count with the working days calculator.
- Total hours worked across days with the timecard calculator.
- Work out how far through a period you are with the percentage calculator.
- Spread a yearly cost across the days with the subscription cost calculator.
Frequently asked questions
How many days are there between two dates?
Subtract the earlier date from the later one. From 17 October 2026 to 25 December 2026 there are 69 days. Tick include the end date to count both days, which gives 70.
Does the calculator include the end date?
By default no, which is how most people count days between dates. Tick Include the end date to count both the first and last day, as is common for hotel nights versus days of a holiday or for inclusive deadlines.
How do I calculate the number of weeks between two dates?
Divide the number of days by 7. 69 days is 9 weeks and 6 days. The result shows the weeks and leftover days.
How many months are between two dates?
The tool gives exact calendar months and days. From 17 October to 25 December is 2 months and 8 days. Months vary from 28 to 31 days, so an average month of 30.44 days is also shown.
Does it handle leap years?
Yes. The count uses real calendar days, so 29 February is included in leap years. From 1 February to 1 March is 29 days in 2024 and 28 days in 2023.
How do I count working days between dates?
The tool counts weekdays, Monday to Friday, between the dates. It does not remove public holidays, which vary by country, so use a working days calculator with a holiday list for exact business-day deadlines.
Can I add days to a date?
Yes. Use the second tab to add or subtract years, months, weeks, days or working days. Adding 100 days to 17 October 2026 gives 25 January 2027.
Can I subtract days from a date?
Yes. Choose Subtract. Taking 90 days from 17 October 2026 gives 19 July 2026.
What happens when I add a month to the 31st?
The day is clamped to the end of the target month. Adding one month to 31 January gives 28 February (29 in a leap year), because February has no 31st.
How many days until Christmas?
The countdown tab shows days, weeks and weekdays left to any date, and a table of the next occurrences of common holidays.
How many days are in a year?
A common year has 365 days and a leap year 366. A leap year occurs every four years, except century years not divisible by 400, so 2000 was a leap year and 1900 was not.
What is the day of the year and ISO week number?
The day of the year counts from 1 January as day 1. The ISO week number follows ISO 8601, where weeks start on Monday and week 1 contains the first Thursday of the year.
Can the end date be before the start date?
Yes. The tool swaps them and tells you, so the count is always positive.
Does it work for dates in the past, such as a birthday or anniversary?
Yes. It works for any dates in the Gregorian calendar. For exact age use an age calculator, which also shows the next birthday.
Does time zone or daylight saving time affect the result?
No. The tool counts whole calendar dates rather than clock times, so daylight saving changes cannot add or remove a day.
Is my data stored or sent anywhere?
No. Everything runs in your browser.
Is this days between dates calculator free?
Yes. It is free to use online with no sign-up.
Sources and further reading
- International Organization for Standardization, ISO 8601 date and time format.
- Time and Date, Date calculators.
- U.S. Naval Observatory, Leap year and calendar information.
- Royal Museums Greenwich, Why do we have leap years?
Sources were consulted in October 2026. Standards and rules can change, so always check the official page for your situation.