How is the age difference calculated?

The calculator subtracts the earlier date from the later date using calendar arithmetic, giving an exact result in years, months, and days — the same way you count someone's age from their birthday.

Can I use dates other than birthdays?

Yes. The tool works with any two calendar dates, such as founding dates of companies, historical events, or project start and end dates.

What if both dates are the same?

If both dates are identical the difference is zero — the tool will display "0 years, 0 months, 0 days."

Does it matter which date I enter first?

No. The calculator always returns a positive difference and tells you which date is earlier, so you can enter them in any order.

Is there a maximum date range supported?

Any dates from the year 100 onward work, up to the latest date your browser's date picker accepts. Years 1 to 99 are not handled correctly, because JavaScript reads a two-digit year as 1900 to 1999.

How does it count months when a date falls on the 29th, 30th or 31st?

If the later month is shorter, the count stops on that month's last day. January 31 to February 28, 2001 is 1 month and 0 days, and January 31 to March 1, 2001 is 1 month and 1 day. Someone born February 29, 2000 is exactly 1 year older than someone born February 28, 2001.

What is the half-your-age-plus-seven rule?

It is a popular rule of thumb, not a law: the youngest partner age it calls acceptable is half your age plus 7. For a 40-year-old that is 27, and for a 30-year-old it is 22. This calculator does not apply the rule. It shows the exact gap between two birth dates, which you can compare against it.

Age Difference Calculator

Enter two birth dates and instantly see the exact age difference in years, months, and days.

Count whole years, then whole months, then the days left over, from the earlier birth date to the later one.

Enter Two Dates

Person A — Date of Birth

Person B — Date of Birth

Result

Enter two dates and click Calculate.

Quick answer

Count whole years, then whole months, then the days left over, from the earlier birth date to the later one. Someone born March 15, 1990 is 5 years, 8 months and 7 days older than someone born November 22, 1995, a gap of 2,078 days. When the start date is the 29th, 30th or 31st and the end month is shorter, the month ends on its last day, so January 31 to February 28, 2001 is exactly 1 month.

Examples

Dates	Age gap	Days
1990-03-15 / 1995-11-22	5y 8m 7d	2,078
1988-06-10 / 1991-02-03	2y 7m 24d	968
1985-12-25 / 1992-12-24	6y 11m 29d	2,556
2001-01-31 / 2001-03-01	0y 1m 1d	29
2000-02-29 / 2001-02-28	1y 0m 0d	365
1970-01-01 / 2026-10-09	56y 9m 8d	20,735

Enter both dates of birth and click Calculate Age Difference.

Summary

The Age Difference Calculator computes the exact gap between two dates in years, months, and days. Enter any two birth dates — or any two calendar dates — and the tool instantly shows who is older, how many years apart they are, and the precise remainder in months and days. All calculation is done in your browser with no data sent to any server.

How it works

Enter the first date (e.g., Person A's birthday) in the top field.
Enter the second date (e.g., Person B's birthday) in the bottom field.
Click "Calculate" or simply change either date to update instantly.
The result shows the total age gap in years, months, and days.
An additional breakdown displays the difference in total months and total days.

Use cases

Find the age gap between two people in a relationship.
Compare ages of siblings, friends, or colleagues.
Calculate the time between any two historical dates.
Determine which of two candidates or applicants is older.
Answer "How many years apart are we?" quickly and accurately.
Verify age-gap eligibility rules in legal or financial contexts.

Frequently Asked Questions

Last updated: 2026-05-29 · Reviewed by Nham Vu