This date calculator will calculate the age of a person on a given test date in years, months, and days, and then show its work so you can perform the subtraction manually when you don't have access to the calculator.
Plus, the calculator will also tell you a person's age rounded to the nearest month, and from there convert the years and months into their age in total number of months.
Note that if you would like a more precise measurement of a person's age, please visit the Age Calculator which converts the number of milliseconds between two dates into years, months, weeks, hours, minutes, and seconds.
For times when you don't have access to a calculator like the one on this page, the following example illustrates how to figure a person's age in years, months, and days using simple subtraction (actual results from calculator).
For our example, suppose the person/student being tested was born on November 30, 1996, and the date the test is being administered is August 7, 2013.
To arrive at the chronological age, we first set up a subtraction problem, where we will subtract the birth date from the test date. Here is how our initial subtraction problem is laid out:
Step #1: As with any other subtraction problem, we start subtracting in the right-most column -- which in this case is the "Days" column:
Since 7 days in the Test row is less than 30 days in the Birth row, we need to borrow 30 days (1 month) from the Test/Months cell, which leaves us with 7 months in the Test/Months cell and 37 days in the Test/Days cell. Subtracting 30 days from 37 days gives us a result of 7 days in the Age/Days cell.
Step #2: Next we move to the Months column:
Since 7 months in the Test row is less than 11 months in the Birth row, we need to borrow 12 months (1 year) from the Test/Years cell, which leaves us with 2012 years in the Test/Years cell and 19 months in the Test/Months cell. Subtracting 11 months from 19 months gives us a result of 8 months in the Age/Months cell.
Step #3: Lastly, we perform the subtraction in the Years column:
Subtracting 1996 years from 2012 years gives us a result of 16 years in the Age/Years cell. Therefore, subtracting the birth date from the test date gives us a chronological age of 16 years, 8 months, and 7 days
Note that I intentionally used two dates that would require borrowing from one column to supplement another so you could see how the borrowing works when subtracting dates. In cases where the top number (test months or days) is greater than the bottom number (birth months or days) you would simply subtract the bottom number from the top number.
With that, let's use the following calculator to subtract a date of birth from a test date.
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To Help You calculate ...
Test date: Select the month, day, and year of the test date.
Birth date: Select the month, day, and year of the date of birth of the person being tested.
Chronological age: This is the result of manually subtracting the entered date of birth from the entered test date.
Age rounded to nearest month: This is the calculated chronological age rounded to the nearest month.
Age in months: This is the calculated chronological age converted into total number of months (from rounded result).