Age Calculator: Years, Months & Days

Age Calculator: Years, Months, Days & Full Time Breakdown

Leap-day birthdays, Western vs Korean age on the same birth date, and a breakdown that counts real month lengths, not 30-day guesses.

What This Age Calculator Does

Forms often want your age on a fixed date, not "as of today." Enter a birth date and an as-of date (today is the default) for years, months, and days, plus totals in weeks through seconds and a countdown to your next birthday. February 29 births count as Feb 28 in non-leap years (the usual legal rule).

Example:

Passport or benefits form due 1 Dec 2026? Set that as the as-of date with your birth date, and you'll see if you've hit the age threshold on that day, not on today's calendar.
What it does not do:

No Korean age, lunar-calendar age, or insurance "age nearest birthday" rounding. Western chronological only (0 at birth, +1 each birthday).

How to Calculate Age from Date of Birth

The age formula

Exact chronological age is computed from the total days between your birth date and the "as of" date, then converted into years, remaining months, and days. Month lengths (28–31 days) and leap years are applied automatically. The algorithm works as follows: start from the birth date, count complete years (checking whether the birthday has passed in the current year), then count remaining complete months, then remaining days.

Leap year rule:

A year is a leap year if divisible by 4, except century years not divisible by 400. This means 2000 was a leap year, but 1900 was not. Each February 29 in the span between your dates is counted.
Leap-day birthdays:

If you were born on February 29, your birthday in non-leap years is treated as February 28 for age-counting purposes, the standard legal convention in most jurisdictions.

Worked example

Birth date: March 15, 1990. As-of date: January 10, 2026.

Complete years: March 15, 1990 → March 15, 2025 = 35 years (birthday has not yet occurred in 2026).
Remaining months: March 15 → January 10 goes backward, so we count from the last birthday: March 15, 2025 → January 10, 2026 = 9 months and 26 days.
Result: 35 years, 9 months, 26 days.
Total days: approximately 13,050 (the calculator counts every day including leap days).

Time units:

Total days are converted to weeks (÷ 7), hours (× 24), minutes (× 60), and seconds (× 60) for the full breakdown display.
Edge case, same-day birth:

If the as-of date equals the birth date, age is exactly 0 years, 0 months, 0 days.

Western vs. Korean and Other Age Systems

Western age is 0 at birth and 1 on your first birthday. Korean age (and some East Asian counts) can add a year at Lunar New Year or from conception, so the same birth date can read a year older. This tool follows Western rules only; the Information Hub in the card covers leap-day handling.

How to Use the Age Calculator

Date of Birth:

Enter your birth date. Use the date picker for easy month/year navigation.
Age at the Date of:

Defaults to today. Change it to find your age at a specific date, a milestone birthday, retirement, or any point in time.
Exact Chronological Age:

Main result shows years, months, and days in bold. Below: total months, weeks, days, hours, minutes, seconds, all locale-formatted.
Next Birthday:

Time until your next birthday (e.g., "5 Months, 12 Days"). Leap-day birthdays use Feb 28 in non-leap years.
Two people:

Need the gap between two birth dates instead of one person's age? Use the Age Difference Calculator for years, months, days, and milestones.

Age Milestones and Legal Ages by Country

Medicare in the US starts at 65; a learner permit can open at 16 in some states. Set the as-of date to the program's cutoff to see if you've passed the birthday, not just whether the calendar year looks right.

United States:

Driving permit: 15–16 (varies by state). Voting and military service: 18. Alcohol purchase: 21. Full Social Security retirement: 66–67 (birth-year dependent). Medicare eligibility: 65.
United Kingdom:

Driving (car): 17. Voting: 18. Alcohol purchase: 18. State pension: 66 (rising to 67 by 2028).
Canada:

Driving: 16 (varies by province). Voting: 18. Alcohol: 18 or 19 depending on province. Canada Pension Plan: early at 60, standard at 65.
European Union (general):

Driving (car): 17–18. Voting: 18 (16 in Austria and Malta). Alcohol: 16–18 depending on country and drink type. Retirement: 62–67 depending on country.
Japan:

Age of majority was lowered from 20 to 18 in 2022. Drinking and smoking remain 20. Driving: 18. National pension: 65.
Australia:

Driving (learner permit): 16. Voting: 18 (compulsory). Alcohol: 18. Age Pension: 67.

Age Calculator FAQ

How do I calculate my age from my date of birth?

Age is the years, months, and days between your birth date and the "as of" date. The calculator uses total days between the two dates, then applies month lengths and leap years to get an exact breakdown (including total weeks, hours, minutes, seconds). See the Information Hub in the calculator for the exact formula and rules.

Why does the second date default to today?

"Age at the Date of" defaults to today so you see your current age right away. Change it to any date to find your age at that moment, milestone birthdays, retirement, or historical events.

How do leap years affect my age in days?

Leap years add Feb 29 every four years (except most century years). Each Feb 29 in your span is counted. Example: born Feb 28, measured Mar 1 in a leap year = 2 days; in a non‑leap year = 1 day.

I was born on February 29. How is my age calculated?

Standard legal practice: leap-day birthdays count as Feb 28 in non-leap years. In 2025 (non-leap), your birthday is Feb 28 for age purposes. The Next Birthday countdown uses the same rule.

What is Western age vs Korean age?

Western chronological age counts from birth: 0 on your birth day, 1 on your first birthday. Korean age (and some East Asian systems) often counts from conception or bumps everyone on Lunar New Year, so a baby can be "1" at birth. This calculator uses the Western standard.

Can I find my age at a future or past date?

Yes. Set "Age at the Date of" to any date. Common checks: "Will I be 59 on our plan year start?" or "How old was I on election day in 2020?"

Age Calculator: Years, Months, Days & Full Time Breakdown

Dates

Totals

How this works

Date used for this calculation

Month lengths and day subtraction

Total days and derived units

Western age vs. other conventions

Leap years and Feb 29

Understanding Your Age

What You Get

Exact breakdown

Next birthday

Any date