Calculate Date Difference
This calculator is intended for general planning and convenience only. For legal, contractual, or official purposes, confirm critical dates with an authoritative calendar.
What is a Date Difference Calculator?
A date difference calculator is a free online tool that calculates the exact duration between two dates. This days between dates calculator helps you determine how many days, months, weeks, hours, and minutes exist from one date to another. Whether calculating time between dates for project planning, age calculations, or event countdowns, our date calculator provides instant, accurate results.
Our calculator also functions as a business days calculator, allowing you to exclude weekends and calculate only working days. This is essential for project management, delivery estimates, and professional scheduling where only weekdays count toward deadlines.
How to Use the Date Difference Calculator
Enter Start Date
Select the beginning date (from date) using the calendar picker or type it manually.
Enter End Date
Choose the ending date (to date). It can be in the past or future.
View Results
Get instant results in multiple formats: years, months, weeks, days, hours, and business days.
How Date Difference is Calculated
Calculating the time between two dates involves more than simple subtraction due to the varying lengths of months and the presence of leap years. Our date calculator uses a precise algorithm to handle these details correctly.
The Calculation Method
Convert to a Common Unit
The easiest way to find the duration is to convert both the start and end dates into a single unit, such as total days or milliseconds from a shared reference point (for example, January 1, 1970 in many systems).
Subtract the Timestamps
Once both dates are represented as a single number, the tool subtracts the start value from the end value to get the total difference.
Convert Back to Readable Units
The result is then converted back into human‑readable formats like years, months, weeks, days, hours, and minutes for display.
Important Considerations
- Leap Years: The algorithm automatically accounts for leap years (years with 366 days), ensuring the extra day in February is included where appropriate.
- Include End Day: By default, the duration is calculated up to, but not including, the end date. Enabling “Include End Day” adds 1 to the total so both start and end dates are counted.
- Time Zones: Calculations are typically based on a consistent time standard (such as UTC) to avoid issues from daylight saving time changes.
Business Days vs. Calendar Days Explained
This calculator can measure time in both calendar days and business days. Knowing the difference helps you plan more precisely for real‑world tasks.
Calendar Days
Calendar days count every day between two dates, including weekends.
- ✓ Includes all seven days of the week.
- ✓ Used for age, event countdowns, and general duration.
- ✓ Example: Monday to the following Monday is 7 calendar days.
Business Days (Working Days)
Business days include only Monday through Friday and ignore Saturdays and Sundays.
- ✓ Excludes weekends.
- ✓ Used for project deadlines, shipping estimates, and business timelines.
- ✓ Example: Monday to the following Monday is 5 business days.
Note: This business days calculator does not adjust for public holidays, which vary by country and region. For official planning, cross‑check with a local holiday calendar.
Practical Use Cases for a Date Calculator
Project Management
Estimate project timelines, sprint durations, and delivery dates using business days for more realistic schedules.
Event Planning
Create countdowns for weddings, vacations, or graduations and see exactly how many days remain.
Human Resources
Determine employee tenure, benefit eligibility dates, notice periods, and probation durations.
Legal and Contracts
Track contract periods, renewal dates, and compliance deadlines accurately.
Personal Milestones
Find your age in days, how long you have been married, or how long you have followed a habit.
Financial Calculations
Measure exact day counts for interest calculations on loans, savings, or investments.
Frequently Asked Questions About Date Calculator
How do I calculate the difference between two dates?
To calculate the difference between two dates, enter your start date and end date in the date calculator. The tool automatically shows the duration in years, months, weeks, days, hours, and minutes, taking leap years and month lengths into account.
How many days are between two dates?
Use this days between dates calculator by entering the two dates. It displays total calendar days, business days, weeks, and other units between them.
What are business days and how are they calculated?
Business days (also called working days) are Monday through Friday. The calculator excludes Saturdays and Sundays when you enable the business days option.
Does the date calculator include the start and end date?
By default, the date difference calculator counts from the start date up to but not including the end date. Turn on “Include End Day” if you want both dates counted.
Can I calculate dates in the past or future?
Yes, you can combine any two dates—past, present, or future—to see how long ago something happened or how many days remain until a future event.
How accurate is the date difference calculator?
The date difference calculator is designed to be very accurate and uses real calendar dates, including leap years and month lengths, rather than approximations.
Tips for Using Date Calculators
Business Planning
For work schedules and delivery estimates, use the business days calculator so weekends are excluded from your timeline.
Leap Year Awareness
Remember that February has 29 days in leap years. The calculator takes this automatically into account so you do not need to adjust manually.
Include End Day Option
If you need both start and end dates counted (for example, days of a hotel stay), enable the “Include End Day” option.
Multiple Time Units
Use days for short spans, weeks or months for medium durations, and years for long‑term planning to make the result easier to interpret.