How to calculate your exact age in years, months, and days.
Calculating your age sounds simple — subtract your birth year from the current year. But the moment you want precision (years, months, days, hours, minutes), the math gets surprisingly complex. Leap years, varying month lengths, and timezone differences all create edge cases that naive calculations get wrong.
Why simple subtraction fails
Consider someone born on February 29, 2000 (a leap day). How old are they on February 28, 2026? Most calculators either crash or give the wrong answer. The correct answer: they're 25 years old — their birthday is considered February 28 in non-leap years.
Or consider someone born on December 31 asking their age on January 1 of the next year. They're 1 day older, but a naive year-subtraction would say they're 1 year older.
The correct algorithm
The proper way to calculate age accounts for whether the current date has passed the birthday in the current year:
1. Calculate the difference in years between birth year and current year.
2. Check if the birthday has occurred yet this year (comparing month and day).
3. If not, subtract 1 from the year count.
4. For months and days, calculate the remaining time after the last birthday.
Handling leap years
A year is a leap year if: it's divisible by 4, AND (it's not divisible by 100, OR it's divisible by 400). So 2000 was a leap year (divisible by 400), but 1900 was not (divisible by 100 but not 400).
For people born on Feb 29, we treat their birthday as Feb 28 in non-leap years — which is the convention used by most governments and legal systems worldwide.
Timezone considerations
If you were born in one timezone and are calculating your age in another, the "current date" may differ. Someone born at 11 PM in New York is already in the next calendar day in Tokyo. Our Age Calculator uses your local timezone to ensure the most accurate result for your location.
Age calculation is a great example of a problem that seems trivial but has real complexity underneath. Our Age Calculator handles all these edge cases correctly — giving you your exact age in years, months, days, hours, minutes, and seconds, with full leap year and timezone support.