Age Calculator

Birth Date
Age at Date

This age calculator can be used to find a person's age given their birthday and a selected date. It will also calculate the time difference between the current date and their previous or next birthday. The calculator can be used for any special occasion, such as anniversaries; simply enter the date of the special occasion into the "Birth Date" field to view the time since the occasion or until the occasion.

How old am I?

A person's age is something that is seemingly simple on the surface, but can be confusing depending on their culture, or how they calculate age. Most typically, a person's age is calculated by subtracting their birth year from the current year; if their birthday has already occurred that year, then the result of the subtraction is their age; if their birthday has not yet occurred, then their age is the current year minus their birth year, minus 1.

To get an even more accurate age, we can take into account smaller increments of time than a year like months and days, as this calculator does. This is slightly more complicated because the different number of days in a month as well as factors such as leap years need to be taken into account. To get even more exact by calculating hours and seconds, the exact birth time must be known, which is something that many people may not know offhand.

However, all of the above assumes that we are solely considering the most common measure of chronological age, which is based on a solar year and the Gregorian calendar, the most widely used calendar system in the world. While virtually everyone in the world uses this definition of age to some degree, certain cultures use other methods to determine chronological age.

Different measures of age

In certain East Asian cultures, rather than a person's age being measured in months for the first year of life, people are considered to be 1 year old at birth. Additionally, rather than age increasing at their birthday, their age increases at the turn of the new year (either on the Gregorian or a lunar calendar). Therefore, in certain extreme cases, such as a person being born 1 day before the turn of the new year, a person who is 1 day old as measured by the Gregorian calendar system may be considered 2 days old the next day in certain East Asian cultures. Three examples include age measurement in China, Taiwan, and Korea.

While age in these countries is also measured using the Gregorian calendar, these countries additionally have their own separate measurements of age.

China & Taiwan—In both China and Taiwan, a child is considered to be 1 year old at birth using their traditional measurement of age. The age of the child increases at the turn of the lunar new year, rather than on their date of birth. Because months in a lunar calendar system are based on the monthly cycles of the Moon's phases, lunar months have different lengths than months based on the Gregorian calendar system. Calendars that are purely lunar vary from solar calendars (like the Gregorian calendar) in that they are 11-12 days shorter than the solar year. For this reason, a child's age will increase at a different date (as measured by the Gregorian calendar) each year. For example, in 2022, the lunar new year occurred on February 1st, while it occurred in February 12th on 2021. These are the dates at which a child's age would increase in these systems. For example, a child who was born on January 31st in 2022 was 1 year old on January 31st and 2 years old on February 1st; meanwhile, using the Gregorian calendar system, the child is only 1 day old.

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