Date Difference Calculator
Find out exactly how many days, weeks, months and years lie between any two dates — including business days and a live countdown to any future date.
What is it?
A date difference calculator computes the exact span of time between two calendar dates. Rather than counting squares on a calendar, you enter a start date and an end date and the tool instantly returns the gap expressed in multiple units: total days, complete weeks (with remaining days), calendar months, years and months, and working days (Monday through Friday, excluding weekends). This free online calculator covers any date range from January 1, 1900 through December 31, 2100 — useful for everything from legal deadlines and contract periods to pregnancy milestones and anniversary countdowns. The "Countdown" mode sets the start date to today automatically, so you can instantly see how many days remain until a future event like a birthday, holiday, exam or project deadline. All calculations happen in your browser using the standard proleptic Gregorian calendar. No data is sent to a server.
How to use it
- Enter the start date in the first date field.
- Enter the end date in the second date field.
- The result panel updates instantly with total days, weeks, months, years and business days.
- Toggle "From today" to lock the start date to the current date for a live countdown.
- Toggle "Include end date" to count both the start and end day (useful for inclusive ranges).
- Toggle "Exclude weekends" to count only Monday–Friday business days.
- Read the natural-language summary: "3 years, 2 months and 14 days" for an at-a-glance answer.
Why use this tool
Time calculations seem straightforward until you factor in variable month lengths, leap years and the difference between calendar months and exact days. How many days between March 15 and November 3? Is that 7 months or 233 days? How many of those are working days if you need to plan a project timeline? Mental arithmetic rarely gets this right, and a spreadsheet formula involves error-prone manual setup. Our date calculator does all of this instantly and shows several representations simultaneously, so you can choose the unit that matters most for your context. Lawyers need total days for limitation periods; HR teams need calendar months for probation periods; event planners need working days; parents counting down to a baby's due date want weeks. The business-day count (Monday to Friday) is particularly useful for planning: it strips out weekends so you can align timelines with actual working capacity. The inclusive/exclusive toggle prevents off-by-one errors in contract and deadline calculations where ambiguity often causes disputes.
Frequently asked questions
Does the calculator account for leap years?
Yes. The calculator uses standard Gregorian calendar rules, including leap years (divisible by 4, except centuries unless also divisible by 400). Any date range spanning a February 29 will include that day in the total.
What is the difference between calendar months and exact months?
Calendar months count the number of month boundaries crossed. The period from January 31 to February 28 is 1 calendar month, even though it is only 28 days. Exact months would be a fractional value. This calculator reports whole calendar months plus remaining days.
Does the business day count exclude public holidays?
The business day count excludes Saturdays and Sundays only — it does not remove public holidays, because holidays vary by country, region and year. For precise working-day calculations with holidays, consult your local calendar.
Can I calculate the difference between dates in the past?
Yes, any date order works. If the end date is before the start date, the tool still returns the difference but labels it accordingly. You can also find out exactly how many days ago a past event occurred.
What does "include end date" mean?
By default, the calculator counts days from the start date up to but not including the end date (exclusive). Enabling "include end date" adds one day to the total — useful for contracts and legal periods where both the first and last day are counted.