Age Calculator
Your exact age in years, months, and days — or the age between any two dates.
About age calculation
This calculator computes the exact elapsed time between two calendar dates, accounting for leap years and variable month lengths. The default second date is today, but you can set any target date — useful for calculating the age of a sample, culture, or patient at a specific timepoint.
Age is usually measured as the amount of time that has passed since a person's birth date. While this sounds simple, different cultures and countries have historically used different methods to calculate age.
How does an age calculator work?
Most age calculators use the international convention of measuring age as the number of complete years, months, and days that have passed since a person's birth date.
For example, if someone was born on June 1, 2000, they turn 25 years old on June 1, 2025.
Modern age calculators compare a birth date with a selected date, usually today's date, and calculate the elapsed years, months, days, weeks, hours, and other time units.
Leap years are automatically considered because they add an extra day to the calendar approximately every four years.
Different age calculation methods around the world
Age is not calculated the same way in every culture. Although most countries now use the international age system, several traditional age counting methods have existed throughout history.
International age system
The international age system is the most widely used method today.
- A person is age 0 at birth.
- Age increases on each birthday.
- Legal documents, medical records, and government systems generally use this method.
Traditional East Asian age counting
Historically, countries such as Korea, China, and Vietnam used age counting systems that differed from the international method.
- A newborn baby may be considered 1 year old at birth.
- Everyone becomes one year older at the beginning of a new year rather than on their birthday.
Because of this, a person's traditional age could be one or two years higher than their internationally calculated age.
South Korea officially adopted the international age system for most legal and administrative purposes in 2023, although traditional expressions of age may still be used informally.
Regarding birthdays in Turkiye
An interesting aspect of birthdays in Türkiye is how age may be expressed. Traditionally, instead of stating your exact age, you may refer to the year of life you are currently living.
- Completed years (doldurmak): If you are exactly 20 years old, you might say that you have "completed" or "filled" your 20th year.
- Ongoing years (gün almak): Once you turn 20, you begin living your 21st year of life. For example, at 20 years and 1 day old, you are considered to be in your 21st year.
- Example: A person who is 25 years old but living their 26th year might say: "I have completed my 25th year and have started my 26th year."
Why age calculator results may differ
Two age calculators can sometimes produce slightly different results depending on how they handle dates and time calculations.
Differences may occur because of:
- Leap years
- Time zones
- Different cultural age-counting systems
- Whether partial months and days are included
- Legal definitions used by specific countries or organizations
- The selected reference date used for the calculation
The Calcorium Age Calculator uses the internationally accepted birthday-based age calculation method.
Interesting age facts
- A person born on February 29 only has a birthday during leap years.
- Someone who is 30 years old has usually lived for more than 10,950 days.
- Age can be expressed in years, months, weeks, days, hours, minutes, or even seconds.
- Many legal rights and responsibilities are tied to specific ages.
Age calculator FAQ
How many days old am I?
An age calculator can estimate the total number of days between your birth date and a selected date.
Do leap years affect age calculations?
Yes. Leap years add extra calendar days that affect the total number of days, weeks, and hours a person has lived.
Why is my Korean age different?
Traditional Korean age counting historically started at age 1 at birth and increased at the start of each new year. This could make a person's age appear one or two years older than their international age.
Is age calculated differently in every country?
Most countries now use the international birthday-based system, but historical and cultural differences still exist.
How accurate is an age calculator?
A well-designed age calculator accounts for leap years and calendar differences to provide accurate results based on the dates entered.
age ← L. aetatem (nom. aetas), contracted from aevitas, from aevum "lifetime, eternity" — the same root as medieval (medium aevum, "middle age") and longevity.