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Date & Time
Date Difference Calculator — Days, Weeks & Business Days Between Two Dates
Count the days, weeks, months and working days between any two calendar dates
A date difference calculator answers a deceptively simple question: how much time is there between two dates? That comes up constantly in everyday American life — counting down to a wedding or vacation, figuring out how many days a project ran, checking a 30-day return window, working out lease or rental periods, or counting the business days before an invoice is due. The trouble is that calendars are messy: months have 28, 30 or 31 days, and February grows a 29th day every leap year. Counting on your fingers gets wrong fast.
The core idea is to convert each date to a count of whole days, then subtract. Total days = end date − start date. From there, total weeks = total days ÷ 7, and the years/months/days breakdown is found by stepping forward from the start date one calendar unit at a time so the result respects the real length of each month.
Here's a worked example. From January 1, 2026 to March 15, 2026: January contributes 31 days, February (2026 is not a leap year) contributes 28, and you land 14 days into March. That's 31 + 28 + 14 = 73 days, which is 10 weeks and 3 days, or about 2 months and 14 days. Switch on "include the end day" and you'd count 74 days instead — useful when both the first and last day count, like a hotel stay or a billing period.
Business days strip out Saturdays and Sundays. Over those same 73 calendar days you'd count 52 weekdays — the number that actually matters for shipping estimates, payment terms ("Net 30" often means 30 calendar days, but "5 business days" never does), and work schedules. Note this tool counts weekdays only; it does not subtract federal holidays, so a true working-day count around Thanksgiving or the Fourth of July will be a day or two lower.
Leap years are the classic trap. A year is a leap year if it's divisible by 4 — except century years, which must be divisible by 400. So 2000 was a leap year, 1900 was not, and 2024 was. Any date span that crosses a February 29 gains an extra day. Miss it and a year-long count comes up short.
The most common mistake people make is the off-by-one: deciding whether the difference includes the final day. "Days between" and "days from-and-including" differ by exactly one. Decide which you mean before you trust the number — that's why this calculator gives you a toggle for it.
This tool is for any two dates. If you want someone's age from a birthday instead, use the dedicated Age Calculator — it's tuned for that.
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Total days = end date − start date (as whole days) • Include end day: add 1 to the day count when both ends count • Total weeks = total days ÷ 7 • Years/months/days = step from start date one calendar unit at a time • Business days = count only Mon–Fri in the span (weekends excluded) • Leap year = divisible by 4, except century years not divisible by 400
📰 Formula
• Total days = end date − start date (as whole days) • Include end day: add 1 to the day count when both ends count • Total weeks = total days ÷ 7 • Years/months/days = step from start date one calendar unit at a time • Business days = count only Mon–Fri in the span (weekends excluded) • Leap year = divisible by 4, except century years not divisible by 400
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Off-by-one: forgetting to decide whether the final day counts.
- Ignoring leap years, so spans crossing Feb 29 come up one day short.
- Confusing business days with calendar days for shipping or payment terms.
- Entering the dates in the wrong order, which flips the sign of the result.
💡 Tips
- For inclusive counts (hotel nights, billing periods), turn on "include the end day."
- Business days here are weekdays only — subtract federal holidays separately for an exact working-day count.
- If you only need someone's age from a birthday, use the Age Calculator instead.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/date-difference-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How do I calculate the number of days between two dates?
Subtract the earlier date from the later one. Convert each date to a day count and take the difference: total days = end − start. For example, Jan 1, 2026 to Mar 15, 2026 is 73 days.
Does this calculator count the end day?
Only if you turn on "include the end day." By default it gives the days between the two dates. Including the end day adds exactly one — use that for hotel stays or billing periods where both ends count.
What are business days and how are they counted?
Business days are weekdays, Monday through Friday. This tool counts every weekday in the span and skips Saturdays and Sundays. It does not subtract federal holidays, so a true working-day count near a holiday will be slightly lower.
How does the calculator handle leap years?
It uses real calendar dates, so February 29 is counted automatically in leap years. A year is a leap year if it's divisible by 4, except century years, which must be divisible by 400. So 2024 and 2000 are leap years; 1900 is not.
Why is the months-and-days result different from total days ÷ 30?
Because months aren't all 30 days. The calculator steps through real months — 28, 30 or 31 days each — so "2 months and 14 days" reflects the actual calendar, not an average month length.
What's the difference between this and an age calculator?
This works for any two dates — a project span, a countdown, a lease. An age calculator is built specifically to measure years, months and days from a birth date to today. Use whichever matches your task.
Can I count the days from a past date to today?
Yes. Enter the past date as the start and today's date as the end. The result tells you how many days, weeks and months have passed since then.
What if I enter the end date before the start date?
The calculator measures the span regardless of order and reports the magnitude, but it's clearest to put the earlier date first. Swapping them only flips the direction, not the number of days.
Are weekends and holidays the same thing here?
No. The business-day count removes weekends (Saturday and Sunday) only. U.S. federal holidays like Memorial Day or Thanksgiving are not removed, so subtract those yourself if you need an exact working-day total.