Date & Time
Date Difference Calculator
Calculate the exact duration between two dates in years, months, weeks, days, and seconds.
Inputs
Results
Total Difference
0 Days
Calendar Breakdown
-
Total Weeks & Days
-
Total Hours / Minutes
-
How It Works
The date difference calculator computes duration by converting calendar inputs to UTC midnight timestamps, performing a subtraction, and mapping the resulting milliseconds to days ($1 \text{ day} = 86,400,000 \text{ ms}$).\n\nTo output years, months, and days, it steps forward incrementally month-by-month and year-by-year from the start date to account for irregular month lengths and leap years.
Formula Used
Total Days = (Date2 − Date1) in Milliseconds / 86,400,000
To find the total calendar days between two dates, the elapsed time in milliseconds is divided by 86,400,000 (the number of milliseconds in a standard 24-hour day).
Y/M/D Difference = IncrementYears(Start) → IncrementMonths(Start) → IncrementDays(Start)
This computes years, months, and days by stepping forward calendar intervals. It accounts for varying month lengths and leap years to provide a human-readable duration.
Worked Example
Here is a step-by-step example of how these values are calculated:
Start Date
Jan 1, 2026
End Date
Feb 15, 2026
Include End Date
Checked
Result: Difference: 46 Days. Calendar Breakdown: 1 month, 15 days. Total hours: 1,104 hrs.
Frequently Asked Questions
What does 'Include end date' mean?
By default, date difference calculations subtract date B from date A, which excludes the boundary of the final day (e.g. Monday to Tuesday is 1 day). Checking this option includes the concluding day, increasing the count by 1 (Monday to Tuesday becomes 2 days).
Does this handle leap years?
Yes. The underlying system uses standard ECMAScript Date models, which correctly parse and count leap days (February 29) when crossing leap years.