Date Duration Calculator.

Find the exact duration between any two dates — in years, months, days, and more.

How to calculate duration between dates.

Calculating the exact duration between two dates requires accounting for the varying lengths of months (28–31 days) and leap years (which add an extra day every four years). Simply subtracting one date from another gives you a total day count, but breaking that into meaningful units like years, months, and days requires careful logic.

Our calculator uses the same proven algorithm as our Age Calculator to handle these complexities. It starts by computing the year and month difference, then adjusts for days by borrowing from the previous month when needed — ensuring the day count is always accurate.

This tool is useful for project planning, tracking milestones, calculating deadlines, determining the length of events, or simply finding out how many days are between two dates.

Frequently asked questions.

Quick answers to common questions about age calculation.

How do I calculate the number of days between two dates?
Enter a start date and an end date in the calculator above. It will instantly show the duration in years, months, days, and also as total days, weeks, hours, minutes, and seconds.
Does the calculator account for leap years?
Yes. The calculator correctly accounts for all leap years when computing the duration between two dates. A leap year adds one extra day (February 29) to the calendar.
Can I calculate duration for dates in the past?
Yes. You can enter any two dates — past, present, or future. The calculator will automatically determine which date comes first and compute the duration between them.
What if I enter the end date before the start date?
The calculator will automatically swap the dates and show the correct duration. It will also indicate that the dates were swapped.
How is this different from the Age Calculator?
The Age Calculator is specifically designed for calculating age from a date of birth. The Date Duration Calculator works with any two dates and does not interpret either as a birth date — it simply computes the time between them.
Can I use this to count business days?
This calculator counts all calendar days including weekends and holidays. It does not currently support business-day-only calculations.

Related tools.

Explore our other free date and age calculators.

Age Calculator

Calculate your exact age in years, months, and days.

Birthday Countdown

Count down the days until your next birthday.

Age Difference Calculator

Compare the age difference between two people.