Date & time
Date Difference Calculator
Pick a start date and an end date to see the gap between them in years, months and days, plus the totals in days and weeks and how many business days (Monday to Friday) fall in between. It's built for the questions Americans ask every day: how many days until a deadline, how many weeks of pregnancy, how long a project ran, or how many working days are left before a closing or filing date. You can toggle between counting the plain gap (excluding the end date) and the whole span (including both endpoints), which matters when a contract or a return window counts the first and last day. Everything updates as you type and runs entirely in your browser, so no dates are uploaded anywhere.
Your dates
Pick a start and end date
Business days count weekdays only and do not account for public or company holidays.
How the date difference calculator works
The total days come from subtracting the two dates' timestamps and dividing by the number of milliseconds in a day. The years / months / days breakdown uses the same borrow method as a calendar age: borrow days from the previous month and months from the year wherever a part goes negative. Business days are counted by walking through every day in the range and keeping only Monday through Friday.
Method
totalDays = (end − start) ÷ 86 400 000 ms totalWeeks = totalDays ÷ 7 businessDays = count of Mon–Fri in [start, end)where: "Days between" counts the gap and excludes the end date "Whole span" includes both endpoints (adds 1 day) weekend days = totalDays − businessDays
Notes & assumptions
- If the end date is earlier than the start date, the dates are swapped so the result is always positive.
- Business days exclude Saturdays and Sundays but not holidays.
- Calculations are for general information only — verify before relying on them.
Worked example
Suppose a project kicks off on January 6, 2025, and wraps up on March 14, 2025, and you want to know how long it ran. Counting the plain gap (excluding the end date) gives 67 days, which is about 9.6 weeks. Broken into calendar units, that's 2 months and 8 days. Now for the working time: of those 67 days, 19 fall on Saturdays or Sundays, leaving 48 business days (Monday through Friday) — useful for estimating billable effort or a delivery window. If instead you needed the whole span, say to count every day a hotel charges you, switch the "Counting" option to include both dates and the day total becomes 68. Note that business-day counts here don't subtract federal holidays such as Presidents' Day, so for payroll or court deadlines you may need to remove those manually.
Frequently asked questions
How do I count the number of days between two dates?
Subtract the earlier date from the later one. The simplest method is to convert each date to a day count and find the difference, which is exactly what this tool does: it takes the two timestamps, divides the gap by the number of milliseconds in a day, and reports whole days. By default it gives the plain gap and excludes the end date, so January 1 to January 8 is 7 days.
Do you include both the start and end dates?
That depends on which mode you pick. The default "Days between" mode counts the gap and excludes the end date, which is how most countdowns and "days until" questions work. The "Whole span" mode includes both endpoints and adds one day, which is how things like hotel nights billed inclusively, vacation days, or some contract and return windows are counted. Switch the Counting option to match how your situation defines the period.
How do I count business days between two dates?
Walk through every day in the range and keep only the weekdays — Monday through Friday — skipping Saturdays and Sundays. This calculator does that automatically and shows the result in the "Business days" row, along with a separate count of weekend days. Keep in mind it counts all weekdays as working days and does not remove public or company holidays, so for legal or payroll deadlines you should subtract those yourself.
Are U.S. federal holidays counted as business days?
Yes, this tool treats every Monday-through-Friday weekday as a business day, including federal holidays like New Year's Day, Memorial Day, Independence Day, Labor Day, Thanksgiving, and Christmas. If you need true working days for a court filing, shipping estimate, or payroll cycle, count how many observed holidays fall inside your range and subtract them from the business-day total.
How many weeks are between two dates?
Divide the total number of days by 7. For example, 67 days is about 9.6 weeks. The tool shows this in the "Total weeks" row with one decimal place, so you can read whole weeks plus the leftover. This is handy for tracking pregnancy weeks, pay periods, or how many weeks a subscription or lease has run.