0 days
Total duration
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What is a Date Duration Calculator?
A date duration calculator measures the amount of time that elapses between two calendar dates. Give it a start date and an end date, and it returns the gap expressed in many useful units at once: total days, full weeks and remaining days, a calendar breakdown in years, months, and days, plus total weeks, hours, minutes, and seconds. It also counts the number of business days — the weekdays from Monday to Friday — in the range. Whether you are counting down to a launch, calculating someone's age, working out a project timeline, or figuring out how many working days a delivery will take, a duration calculator removes the error-prone manual arithmetic of subtracting dates by hand.
How to Use This Calculator
- Pick a From date using the first date field. It defaults to today.
- Pick a To date in the second field. The result updates live as you change either date.
- Read the headline result — the total number of days between the two dates — and click it to copy it to your clipboard.
- Scroll the result grid for the full breakdown: weeks and days, years/months/days, and totals in weeks, hours, minutes, seconds, and business days.
- Optionally tick Include time of day to add hour-and-minute precision to each date for an exact down-to-the-minute duration.
- Use the quick buttons to jump to common ranges such as the current year so far, or the days remaining until the next New Year. The Swap dates button reverses the two dates.
The two dates are stored directly in the page address as you type, so you can copy the URL from your browser's address bar and share a pre-filled calculation with anyone. Everything runs in your browser — no dates are ever sent to a server.
Business Days Explained
Business days, sometimes called working days, are the days of the week when most offices, banks, and shipping carriers operate: Monday, Tuesday, Wednesday, Thursday, and Friday. Saturdays and Sundays are weekend days and are excluded from the count. Business-day math matters whenever a timeline is quoted in working days rather than calendar days — shipping estimates ("delivered in 3–5 business days"), payment terms ("net 30 business days"), notice periods, and service-level agreements all commonly use working days.
This calculator counts every weekday that falls in the range between your two dates. Keep in mind that it counts weekdays only and does not subtract public holidays, because holidays differ from country to country and even from region to region. If your jurisdiction observes holidays inside the range, the true number of working days will be slightly lower than the figure shown. For most planning purposes the weekday count is the right starting point, and you can subtract the handful of holidays that apply to you.
How the Math Works
All arithmetic in this tool is done in Coordinated Universal Time (UTC). This is a deliberate choice. Local time zones observe daylight saving time, which makes one day in spring only 23 hours long and one day in autumn 25 hours long. If you do date subtraction in local time across one of those boundaries, you can end up one day short or one day over — a classic off-by-one bug. Because every UTC day is exactly 24 hours, computing the difference in UTC guarantees the day count is always correct.
The total days figure is the plain difference between the two dates. The years / months / days breakdown is calendar-aware: it counts whole years, then whole months, then leftover days, borrowing from the previous month when a day count goes negative. This handles the fact that months have different lengths and that February is shorter in non-leap years, which a naive "divide by 30" approach cannot do. By default the duration is exclusive of the end date — January 1 to January 2 is one day — which matches how most people count nights and elapsed time. Add one day if you need an inclusive count of both endpoints.
Common Uses
- Age and anniversaries — how many years, months, and days old someone or something is.
- Project planning — total calendar days and working days between a kickoff and a deadline.
- Shipping and logistics — estimating arrival from a business-day window.
- Billing and contracts — counting days in a billing period or notice window.
- Countdowns — days remaining until an event, exam, holiday, or release.
- Subscriptions and trials — verifying how long a free trial or term actually lasts.
Frequently Asked Questions
How do you calculate the number of days between two dates?
Subtract the earlier date from the later date and divide the millisecond difference by the number of milliseconds in a day (86,400,000). This calculator uses UTC-based math so that daylight saving time changes never add or remove a day. For example, from 2026-01-01 to 2026-12-31 is exactly 364 days.
Does the date duration calculator include the end date?
By default the result is the exclusive difference — the end date is not counted as a full day. The duration from January 1 to January 2 is 1 day. If you want to count both the start and end days (inclusive), add 1 to the total days. This is common when counting things like hotel nights versus calendar days.
What are business days?
Business days, also called working days, are the weekdays Monday through Friday. Saturdays and Sundays are excluded. This calculator counts the number of weekdays in the range, which is useful for estimating delivery times, project deadlines, and payment terms. Note that it does not account for public holidays, which vary by country.
How are years and months calculated in the breakdown?
The years/months/days breakdown is calendar-aware. It counts whole years first, then whole months, then leftover days, borrowing from the previous month when needed. Because months have different lengths, this is more accurate than dividing total days by 30 or 365. For example, one calendar year is shown as 1 year, 0 months, 0 days regardless of leap years.
Why use UTC for date math?
Local time zones observe daylight saving time, which makes some days 23 or 25 hours long. Doing date arithmetic in local time can therefore produce off-by-one errors at the spring-forward and fall-back boundaries. Computing in UTC, where every day is exactly 24 hours, guarantees the day count is always correct.
Can I share my calculation?
Yes. The two dates you enter are encoded in the page URL as you type, so you can copy the address bar and send it to anyone. When they open the link, the calculator loads with the same dates already filled in and the result computed.