Date Difference Calculator
Last updated: September 23, 2026
Find the exact time between two dates in days, weeks, months, and business days.
Pick a start and end date. Get the calendar difference plus total days, weeks, months, and business-day count.
How the date difference is calculated
Pick a start date and an end date. The end date has to fall on the start date or after it. The calculator then reports the span in several units that answer different questions.
Total days is the number of days from the start date up to the end date: 1 January to 2 January is 1 day, and the same date in both fields is 0 days. Total weeks is how many full 7-day groups fit in that day count. Leftover days are dropped from the weeks figure, so 10 days displays as 1 week even though 3 days remain. You can see those leftover days by comparing weeks × 7 with the total-day count.
The readable line is a calendar walk: completed years, then completed months, then the leftover days. If the end day-of-month is earlier than the start day-of-month, the count borrows a month and adds the length of the previous month, which is 28, 29, 30, or 31 depending on the month and on leap years. The "total months" figure is those completed years turned into months, plus the leftover months. It is not total days divided by 30.
Business days count Monday through Friday from the start date through the end date, including both ends when they fall on a weekday. Saturday and Sunday are skipped. Holidays are not skipped. A Monday-through-Friday span is 4 total days and 5 business days. A single weekday entered as both dates is 0 total days and 1 business day.
Worked examples
Example 1: Two months that include a leap day
Start 15 January 2024, end 15 March 2024. The readable difference is 2 months and 0 days. Total days is 60, because 2024 is a leap year and 29 February sits inside the span. Full weeks: 8, because 60 ÷ 7 is 8 with 4 days left over. The weeks field shows 8. The 4 leftover days are still inside the total-day count.
Example 2: A one-year anniversary in a leap year
Start 1 January 2024, end 1 January 2025. The calendar line is 1 year, 0 months, 0 days. Total days is 366, not 365, because 2024 contains 29 February. Full weeks: 52. The inclusive Monday–Friday count for that same span is 263 business days. A contract that says "one year from 1 January" usually means the anniversary date. A contract that says "365 days" means a different end date in a leap year. Read the noun in the agreement before you treat these figures as the same.
Example 3: A work week, inclusive
Start Monday 1 January 2024, end Friday 5 January 2024. Total days is 4. Business days is 5, because both Monday and Friday are included and none of those five dates is a weekend. If your project plan says the kickoff day is not a working day, subtract one from the business-day count. If a holiday falls on one of those weekdays, subtract that day too. This tool will not subtract it for you.
Example 4: Employment tenure
A start date of 3 June 2019 and an end date of 3 June 2024 reads as 5 years, 0 months, 0 days. That is the calendar length of the appointment. Human resources may also care whether the final day was worked, whether weekends count toward a probation period, and which holidays the handbook lists. Use the business-day number as the raw weekday count, then cross off the handbook's holidays by hand.
Example 5: Choosing the right time tool
A span of dates belongs here. "How old will I be on that date" belongs on the Age Calculator, which adds a next-birthday countdown. Hours between two clock times belong on the Time Duration Calculator. A weekly timesheet belongs on the Time Card Calculator with Lunch Breaks. A live "time remaining" clock belongs on the Countdown Calculator. When a deadline is stated in hours instead of dates, such as a 72-hour window, the countdown page has a table of common lengths in total hours.
When to use this
Use it for project deadlines, rental or contract terms, school-break length, probation periods, and the number of days between two events on a calendar. It is a planning aid. Clinicians date pregnancies with their own rules and ultrasound, so a day count between two dates is not a due-date opinion. Lenders and courts follow the wording of the document in front of them; quote that wording next to the number you compute.
Common mistakes
- Mixing inclusive and exclusive counts. Total days is the gap between the dates. Business days includes both endpoints when they are weekdays. "Within 30 days" in a contract may or may not count the start date. Match the document.
- Reading total months as days divided by 30. The months figure follows the calendar. January 31 to March 31 is two calendar months even though the day count is 60 in a leap year and 59 otherwise, depending on February.
- Assuming holidays are removed. Only Saturday and Sunday are removed from the business-day count. Thanksgiving, Christmas, and a company shutdown stay in the number until you subtract them.
- Swapping the dates. If the end is earlier than the start, the calculator stops and asks you to reorder them. The length is the same either way; put the earlier date first.
- Using date fields for a shift. There is no time of day. A night shift that crosses midnight is a clock problem, not a calendar problem.
Limitations
No holiday calendar, no time of day, and no time-zone conversion. Daylight-saving changes do not affect a date-only count. The weeks field discards a remainder shorter than 7 days. The tool does not count backward and does not produce a negative span. Very long ranges are still a day count between the two dates you picked; verify the years if you typed them quickly. For an age in years, months, and days plus the next birthday, use the age calculator so you do not have to interpret a generic span as a birthday.
FAQ
Does 29 February count?
Yes, when it falls strictly inside the span or on one end in the way the day count works. From 1 January 2024 through 1 January 2025 the total is 366 days. From 1 January 2025 through 1 January 2026 the total is 365 days, because 2025 is not a leap year.
Why can business days be higher than total days?
On a short weekday span, the business-day count includes both the start date and the end date, while total days is the number of days between them. Monday to Friday is 5 weekdays and 4 days of gap. Across a weekend the relationship flips, and business days fall below the calendar-day gap.
How do I remove holidays?
List each holiday that lands on a Monday–Friday inside the span, including the start or end date if people had that day off, and subtract those dates from the business-day result. A federal holiday that falls on a Saturday may be observed on Friday; subtract the day people actually had off, not the ceremonial date, if the question is about staffing.
Is the end date included?
In the business-day count, a weekday end date is included. In the total-day count, the figure is the elapsed days from start to end, so a same-day pair is 0. Say which figure you are quoting when you send the number to someone else.
Can I measure a pregnancy or a legal deadline here?
You can measure the number of days between two dates you already have. Medical dating and legal deadlines add rules this page does not know: gestational wheels, "business day" definitions in a statute, and filing cutoffs at a particular hour. Use the day count as arithmetic, then apply the rule from the clinic or the document.
Practical tips
Write "calendar days" or "weekdays, holidays still included" next to the number before it goes into an email. If a deadline is "ten business days after approval," start on the approval date, run the inclusive weekday count, and then decide whether the approval day itself counts under that policy. Subtract planned time off after you have the raw weekday total so vacation is visible as its own line.
For a lease or a subscription, compare the calendar line with the day count. "One year" that crosses 29 February is 366 days. Billing systems that add 365 days will land on a different end date. Knowing both numbers makes the invoice easier to challenge or to accept.
When you only need hours, leave this page. Combining a date span with a clock span is how people double-count an overnight shift. Dates here, clocks on the duration or work-hours tools.