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Age Calculator Online by Date of Birth Or Between Two Dates

This online age calculator is used to calculate the age between two dates or by date of birth. This tool is used to calculate age in years, months, and days from one date to another, from date of birth to current date, or until death.

How Age is Calculated

The age of an individual on Earth is determined by the number of Earth years since their birth. This is calculated by measuring the number of times the planet has revolved around the Sun. If we were to inhabit a planet in the Solar System other than Earth, our age would be recorded differently due to each planet taking a variable amount of time to orbit around the Sun. Therefore, each heavenly body has its own individual year length.

There are actually two definitions of day:

1. Sidereal day is the time of rotation of the Earth relative to the stars.

2. Solar day is the time of rotation of the Earth relative to the Sun.

The standard of reckoning time throughout the day is the 'mean day' that has been established to have a period of 24 hours. On Earth, the solar and sidereal days are almost identical in length, with the solar day lasting three minutes and fifty-four seconds longer. This is why stars appear to rise approximately four minutes earlier each night.

Here is a formula to calculate your actual age

The general formula that many of us learn is rather simple and appealing. When you need to determine age in years and you want a fractional age (continuous values), a fairly well accepted industry standard approximates leap years with a quarter day each year

AGE=int((NOW - DOB)/365.25);

First determine the number of days from DOB to NOW, then divide by the number of days in a year. Because we have leap years, we use 365.25 as an average number of days in a year. Since AGE is always a whole number, we then use the INT (or FLOOR) function to grab just the integer portion of the result. This generally produces an accurate value for age, making it a nice solution for most applications.

Depending on how leap years fall relative to the date of death and birth, the approximation could be off by as much as what is essentially two days over the interval. Over a person’s lifetime, or even over a period of just a few years, two days will cause an error in at most the third decimal place.

Leap Year is the game changer - if all years had 365 days, then we could just divide by 365, and the formula would always produce a correct value for age.


Society thinks of age as whole years, with ‘credit’ withheld until the date of the anniversary of the birth. The following equation (first proposed by William Kreuter) measures age in whole years. It counts the months between the two dates, subtracts one month if the day boundary has not been crossed for the last month, and then converts months to years. Cake Disposable

Age Calculator

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