Date Difference Calculator
Calculate the exact time between any two dates in days, weeks, months, years, and business days.
What Is a Date Difference Calculator?
A date difference calculator is a tool that calculates the exact time span between any two dates. Unlike an age calculator (which focuses on birth dates), a date difference calculator can be used for any dates – project timelines, historical events, vacation planning, contract durations, and more.
This calculator provides the date difference in multiple formats:
- Years, months, and days – Precise breakdown of the time span
- Total days – The complete number of days between dates
- Total weeks – How many complete weeks fit in the time span
- Total hours and minutes – For precise time measurements
- Business days – Excluding weekends (Monday-Friday only)
How to Calculate Days Between Two Dates
Calculating the difference between two dates is straightforward:
- Enter the start date – Select the beginning date
- Enter the end date – Select the ending date
- Choose whether to include the end date – This affects the total by 1 day
- Results appear automatically – See instant results in multiple formats
The calculator will show you the difference in years, months, days, total days, weeks, hours, and business days.
How to Calculate Business Days Between Two Dates
Business days (also called working days or weekdays) exclude weekends. To calculate business days:
- Count all days between the two dates
- Subtract all Saturdays and Sundays
- (Optionally) Subtract public holidays
Formula: Business days = Total days - Weekend days - Holidays
Example: From Monday, Jan 1 to Friday, Jan 12 (12 calendar days) = 10 business days (excluding 2 Saturdays and 2 Sundays)
Our calculator automatically calculates business days for you by excluding weekends. For a more advanced business days calculator that includes holiday exclusions, see our Working Days Calculator.
Should I Include the End Date in the Calculation?
Whether to include the end date depends on your use case:
- Include end date: If you're counting "days in a range" (e.g., Jan 1-3 = 3 days: Jan 1, 2, 3)
- Exclude end date: If you're counting "days elapsed" or "days until" (e.g., from Jan 1 to Jan 3 = 2 days elapsed)
Examples:
- Project duration: Include end date (first day to last day, inclusive)
- Days until deadline: Exclude end date (how many days remain)
- Age calculation: Exclude end date (years elapsed)
- Rental period: Include end date (first night to last night, inclusive)
How Many Weeks Between Two Dates?
To convert days to weeks, divide the total days by 7:
Formula: Weeks = Total Days ÷ 7
Examples:
- 30 days = 4 weeks, 2 days (4.29 weeks)
- 60 days = 8 weeks, 4 days (8.57 weeks)
- 90 days = 12 weeks, 6 days (12.86 weeks)
Our calculator shows both complete weeks and the decimal representation for precision.
How Many Months Between Two Dates?
Calculating months between dates is more complex than days because months have varying lengths (28-31 days):
- Complete months: Full calendar months between dates
- Approximate months: Total days ÷ 30.44 (average month length)
- Exact months and days: Precise breakdown (e.g., 2 months, 15 days)
Our calculator uses the exact method, accounting for varying month lengths and leap years.
Calculate Difference for Historical Dates
The date difference calculator works for any dates, including historical events:
- July 4, 1776 to today: America's age since independence
- December 7, 1941 to today: Years since Pearl Harbor
- July 20, 1969 to today: Years since the moon landing
- September 11, 2001 to today: Years since 9/11
This is useful for anniversaries, commemorations, and historical research.
Calculate Days Until a Future Date
Use this calculator to find how many days until important future events:
- Vacation countdown: Days until your trip
- Project deadline: Days remaining to complete work
- Birthday countdown: Days until your birthday
- Holiday countdown: Days until Christmas, New Year's, etc.
- Retirement countdown: Days until retirement
For a live countdown timer, see our Time Until Calculator.
People Also Search For
How many days between two dates?
To find the number of days between any two dates, enter both dates in the calculator above — the result shows the total days, plus a breakdown in weeks, months, and business days. The calculator also lets you toggle whether to include the end date in the count, which changes the result by one day depending on whether you need an inclusive or exclusive range.
Calculate time between dates in months and years?
The calculator shows the full breakdown of the time between two dates in years, months, weeks, and days simultaneously — for example, "1 year, 4 months, 2 weeks, 3 days." This multi-unit view is especially useful for contract durations, lease periods, project timelines, and any situation where you need to express a date range in human-readable terms rather than just a raw day count.
How many weeks between two dates?
The number of weeks between two dates equals the total days divided by 7 — for example, 30 days is 4 weeks and 2 days, or 4.29 weeks. The calculator does this automatically and displays both the decimal representation (e.g., 4.29 weeks) and the whole-weeks-plus-remaining-days breakdown (e.g., 4 complete weeks, 2 days) so you get the most useful format for your situation.
Date range calculator with business days?
The working days option in this calculator excludes Saturdays and Sundays to give you the number of business days (Monday through Friday) between two dates. This is useful for project planning, calculating invoice payment windows, estimating shipping timelines, and any scenario where weekends don't count. For a more advanced version that also excludes US federal holidays, use the Working Days Calculator.
How to calculate date difference in Excel?
In Excel, the DATEDIF function calculates date differences: =DATEDIF(A1,B1,"D") gives total days, =DATEDIF(A1,B1,"M") gives total months, and =DATEDIF(A1,B1,"Y") gives total years. You can also use simple subtraction (=B1-A1) to get total days directly. However, getting the full breakdown in years, months, weeks, and business days requires multiple nested formulas. The calculator on this page gives all of those units instantly with no formula setup required.
What is the date difference formula?
The simplest date difference formula is: end date minus start date equals the number of days between them. In practice, converting that day count into years and months is where complexity arises — months have 28 to 31 days, and years have 365 or 366 days, so the conversion isn't a fixed ratio. This calculator handles all of that complexity automatically, using calendar-accurate math to give you the exact breakdown in every unit without rounding errors.