Date Duration Calculator: Days Between Two Dates
Date span and calendar shift
Measure a stretch of calendar days or move a date forward and back by a chosen amount.
Compare two dates
Choose a start and end date to see the interval.
Interval totals
- Total days
- Weeks and days
- Decimal weeks
- Calendar duration
- Weekdays
- Weekend days
- Hours
- Minutes
- Seconds
Calendar days x 24; no daylight-saving adjustment.
The end date is earlier than the start date, so the interval is shown in reverse.
Weekdays are Monday to Friday only. Public holidays are not excluded.
Counting rule: by default, the earlier date is counted and the later one is left out. Turn on the final-date option to count both ends. The same dates determine total days, weekdays and weekend days; equal dates normally span zero days. Calendar parts use complete clamped months first, then leftover days. All calculations use Gregorian calendar dates rather than clock time.
Try a sample
Move a date by an amount
Enter a reference date and a whole-number amount.
New date
- Written date
- ISO date
- Distance moved
The day was adjusted to the last day of the month.
Day and week choices move by a fixed number of calendar dates. Month and year choices move by calendar months, keeping the day number when possible and capping it at month-end otherwise. Use a whole number from 0 through 1,000,000; comma-grouped digits are also accepted. Results must remain within years 1583–9999.
Try a sample
This date duration calculator counts the exact days between two dates and also shows weeks, calendar years, months, weekdays, hours, minutes and seconds. A second panel adds or subtracts days, weeks, months or years from any date. For example, 1 January to 31 December 2025 is 364 days, or 365 days when you count both dates.
What the Date Duration Calculator Does
Pick two dates and the tool returns the gap in several forms at once. Total days suit deadlines and contracts, calendar years, months and days read naturally in plain language, and weekday counts help with work planning. The calculator uses plain calendar dates, so your time zone and daylight saving never add or remove a day.
How to Use the Date Duration Calculator
Days between two dates
- Choose a start date. Type it, use the date picker, or press “Today”.
- Choose an end date. Use the same options.
- Decide whether to count the final date. Tick “Include the final date” to count both ends of the range.
- Read the results. They appear instantly, with no need to press a button.
- Swap if needed. “Swap dates” exchanges the two fields in one click.
Adding or subtracting a duration
- Set a reference date. This is the date you start from.
- Pick Add or Subtract. The operation decides the direction of travel.
- Enter an amount. Use a whole number from 0 to 1,000,000. Commas such as 1,000 are accepted.
- Choose a unit. Days, weeks, months or years are available.
- Read the new date. It appears as a written date and in the ISO format of year, month and day.
Use “Copy results” to keep the numbers, and “Reset” to clear a panel.
How the Counting Works
The same simple rules apply every time, so the totals always agree with each other.
- Total days = end date minus start date. Equal dates give 0 days, and consecutive dates give 1 day.
- Include the final date adds one day, which counts both the first and last dates.
- Weekdays are Monday to Friday inside the same counted days, and the rest are weekend days.
- Calendar duration takes the most whole months that fit between the dates, then shows the leftover days.
- Moving by months or years keeps the day number when it exists and uses the last day of the month when it does not.
If the end date is earlier than the start date, the calculator shows the same interval in reverse and tells you so. Dates between the years 1583 and 9999 are supported, using the Gregorian calendar.
Worked Examples
A full calendar year
Count from 1 January 2025 to 31 December 2025. The default total is 364 days, which is 52 weeks and 0 days, and the calendar duration is 0 years, 11 months and 30 days. Tick “Include the final date” and the result becomes 365 days, which is exactly 1 year, 0 months and 0 days.
Days after sowing
Planning a field trial? Take a sowing date of 15 March 2026 and add 90 days. The new date is Saturday, 13 June 2026. The same panel works for days after treatment, days to harvest or reporting deadlines.
A long interval
From 1 January 2000 to 12 October 2026 is 9,781 days. That equals 1,397 weeks and 2 days, or 26 years, 9 months and 11 days. Of those days, 6,985 are weekdays and 2,796 fall on weekends.
Counting working days
Count from Monday 12 October 2026 to Friday 16 October 2026. The default result is 4 days and 4 weekdays, because the final Friday is left out. With the final date included, the result is 5 days and 5 weekdays.
A month-end date
Add 1 month to 31 January 2026. February has only 28 days that year, so the answer is Saturday, 28 February 2026, and the tool notes that the day was adjusted. Adding 1 year to 29 February 2024 lands on Friday, 28 February 2025 in the same way.
Hours, minutes and seconds
A gap of 30 days equals 720 hours, 43,200 minutes and 2,592,000 seconds. These figures multiply whole calendar days by 24, 1,440 and 86,400. They do not adjust for daylight saving.
Common Use Cases
- Project deadlines. Measure how long a task runs, or find a milestone date from a start date.
- Research and field work. Track days after sowing, treatment dates and trial lengths.
- Contracts and notice periods. Show elapsed time either as one number of days or as years, months and days.
- Work scheduling. See how many weekdays sit inside a range, keeping in mind that public holidays stay in the count.
- Age and anniversaries. Find exactly how long ago something started.
Planning a crop? The Garden Planner Calculator adds days to maturity to your planting date. Turning working time into pay? Try the Hourly to Salary Calculator.
Tips for Reliable Results
- Pick total days when you need the precise length of a span.
- Pick the calendar duration when a plain-language answer in years and months suits you better than a long day count.
- Decide in advance whether the last day should count, since it changes every total by one.
- Look closely at answers near the end of a month, because short months pull the day back to their final date.
- Remember that the weekday figure ignores public holidays.
Common Mistakes to Avoid
- Reading the weekday figure as a count of working days, since holidays are not removed
- Forgetting that the default count leaves out the final date
- Expecting every month to be the same length
- Comparing total days with calendar months and expecting matching numbers
- Mixing up day and month when typing a date by hand
Frequently Asked Questions
How are the days between two dates calculated?
The calculator turns each date into a whole day number and subtracts them. Because it never uses clock times, a daylight saving change cannot shift a result by an hour.
Are the start and end dates both counted?
Unless you tick “Include the final date”, the last date is left out, so equal dates give 0 days and consecutive dates give 1 day. Ticking the option counts both selected dates.
Does the weekday count exclude public holidays?
No. Every Monday-to-Friday date counts, even when it is a public holiday, because the tool has no holiday calendar.
What happens when I add a month to January 31?
The result lands on the final day of February, which is the 28th or the 29th depending on the year. The tool shows a note whenever it adjusts the day.
Why does the calendar duration differ from the total days?
Total days is one continuous count, while the calendar duration splits the gap into whole months and leftover days. Months have different lengths, so the two views read differently.
What if the end date is before the start date?
The tool shows the same interval as if the dates were swapped and adds a note explaining this. You can also use “Swap dates”.
Which years does the calculator support?
It supports dates from the year 1583 to the year 9999 on the Gregorian calendar. Results that fall outside this range show an error instead of a date.
Does the calculator store or send my dates?
No. Everything is calculated in your browser, and nothing is stored, so use “Copy results” if you want to keep a figure.
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