Age Calculator: Years, Months & Days

Date used for this calculation

The "Age at the Date of" field uses February 25, 2026 (2026-02-25). When it defaults to today, this is the current date at page load. Change the date above to see your age at any point in time.

Leap Year Factor

The calculation factors in an extra day for every February 29th encountered in the date range between your birth and the "as of" date. Leap years occur every four years (except most century years), so someone born in 1992 and measured in 2026 has lived through several Feb 29ths—each one adds a day to the total.

Month lengths and day subtraction

Months have 28, 29, 30, or 31 days. When subtracting dates, we borrow from the previous month: if the day-of-month on the “as of” date is less than the day-of-month on the birth date, we subtract one month and add the number of days in that previous month to the day difference. This yields an accurate “years, months, and days” remainder.

Total days = end date − start date in milliseconds, divided by 86,400,000 (ms per day). Total weeks, months, hours, minutes, and seconds are derived from that span.

Understanding Your Age

Exact age needs leap years, variable month lengths, and precise day counts handled correctly. These notes explain how the calculator gets your chronological age from any two dates.

How Time is Tracked

Leap Years

A tropical year is ~365.2425 days. The calendar adds February 29 every four years (except most century years) to stay aligned. The calculator counts every Feb 29 in your span—your total days are exact.

Month Variation

Months run 28–31 days. When subtracting dates, we borrow from the previous month so the years-months-days remainder is correct—no rounding to 30 days.

Time Units

Beyond years and months: total weeks, days, hours, minutes, and seconds. Handy for "How many seconds have I lived?" or "Hours until my next birthday?"

Leap Day Birthdays

Born on Feb 29? We use Feb 28 in non-leap years—standard legal practice. The Next Birthday countdown and age-at-date logic follow the same rule.

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

Calculate age from date of birth. Exact chronological age in years, months, days plus total weeks, hours, minutes, seconds. Leap years and leap-day birthdays handled. Next birthday countdown. Western age. Free, runs locally, no sign-up.

How to Calculate Age from Date of Birth: The Complete Formula

Exact chronological age starts with total days:

\text{Total days} = \frac{\Delta t_{\text{ms}}}{86{,}400{,}000}

where Δt is the millisecond difference between end and start. From that we derive years, remaining months, and days—accounting for month lengths (28–31 days) and borrowing when day-of-month goes negative. Leap years add Feb 29 every four years; the calculator includes each Feb 29 in your span. Born on a leap day? We use Feb 28 in non-leap years (standard legal practice). Result: exact age in years, months, days, plus total weeks, hours, minutes, seconds.

Western Chronological Age vs. Korean Age and Other Systems

The Western chronological age (what this calculator uses) counts from birth: you're 0 on your birth day and turn 1 on your first birthday. Korean age and some East Asian systems count from conception or bump everyone on Lunar New Year—a baby can be "1" at birth. Same dates, different numbers. This tool follows the Western standard: birth date to "as of" date, with leap years and month-length handling applied correctly.

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.

Age Calculator FAQ

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

Age is full years, remaining months, and days between your birth date and the "as of" date. Total days:

\text{Total days} = \frac{\Delta t_{\text{ms}}}{86{,}400{,}000}

where Δt is the millisecond difference. The calculator handles leap years and month lengths, then derives weeks, days, hours, minutes, seconds.

? 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 for your exact age at that moment. Handy for retirement planning, "How old will I be in 2030?", or contractual age checks.

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

Define Dates

Total Breakdown

Information Hub

Understanding Your Age

How Time is Tracked

Leap Years

Month Variation

Time Units

Leap Day Birthdays

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

How to Calculate Age from Date of Birth: The Complete Formula

Western Chronological Age vs. Korean Age and Other Systems

How to Use the Age Calculator

Age Calculator FAQ

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

? Why does the second date default to today?

? How do leap years affect my age in days?

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

? What is Western age vs Korean age?

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

Time & Date Reference Note