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Age Difference Calculator

Enter two birth dates to see the exact gap between them in years, months and days. The dates stay in your browser.

How do you work out the age difference between two people?

Compare the two birth dates on the calendar: count the full years first, then the full months, then the days left over. Someone born on 4 May 1990 and someone born on 16 December 1994 are 4 years, 7 months and 12 days apart, and always will be.

Person 1

Person 2

Both dates are used only on this device. Nothing is saved and nothing is shared.

Your result will appear here after you press Calculate.

How the age gap is worked out

The earlier birth date is the starting point. The calculator counts complete years to the later birth date, then complete months, then the remaining days. This is the same calendar arithmetic used by the Age Calculator and the Date Difference calculator, so all three agree.

Years, months and days compared with total days

Two people four years apart can be 1,460 or 1,461 days apart depending on how many leap years fall between their birthdays. Both figures are correct, they just answer slightly different questions. Use years, months and days when you are talking to people, and total days when you need the raw count.

Leap-day birth dates

A 29 February birth date is treated as a real date. In years without a 29 February, the month boundary is reached on 28 February, which is what most legal and administrative systems use.

Worked examples

  • 4 May 1990 and 16 December 1994: 4 years, 7 months, 12 days.
  • 1 January 2000 and 2 January 2000: 1 day.
  • 29 February 2000 and 1 March 2001: 1 year, 1 day, which is 366 total days.
  • Identical birth dates: same age, with a zero gap.

Privacy

Birth dates are personal, so this page keeps them local. There is no share link containing dates, no storage, and no analytics event that carries what you typed.

Related tools

Age CalculatorCalculate exact age from any date of birth.Open Date Difference CalculatorCount days, weeks, months, and years between two dates.Open Days Until CalculatorCount how many days are left until any future date.Open Months Between Dates CalculatorCount whole calendar months and the days left over.Open

Frequently asked questions

How is the age difference between two people calculated?
Count the whole years between the two birth dates, then the whole months, then the leftover days. The gap is fixed: two people born four years apart stay four years apart for life.
Why do total days and calendar years not line up?
Calendar years vary because of leap years. Four calendar years can be 1,460 or 1,461 days. The years, months and days figure follows the calendar, and the total days figure counts actual days.
What happens with a leap-day birth date?
29 February is handled as a real date. When the other date falls in a non-leap year, the month boundary is reached on 28 February, which is the usual convention and matches the Age Calculator.
Are the birth dates sent anywhere?
No. The calculation runs in your browser. Birth dates are not stored, not sent to analytics and not included in any share link.
How is this different from the Age Calculator?
The Age Calculator takes one birth date and tells you how old that person is today, which changes daily. This page compares two birth dates and gives a gap that never changes.

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Calcadian calculators are for general planning and informational use. Please verify critical deadlines, legal, payroll, tax, HR, or official requirements with the relevant authorities or a qualified professional.