How Old Are You Exactly? - Age Calculator

Age calculator finds the age based on the date of birth and tells, how old are you exactly. It is an online calender tool specially programmed to find the exact age of a person or an animal. The calculated age is displayed in terms of years, months, days, hours, minutes, and seconds. It also calculates our next birthday from date of birth using.
It is necessary to follow the next steps:

1. Enter your birthday in the corresponding format: month/day/year. The month must be in the interval `[1, 12]`, a day of the month must be in the interval `[1, 31]` and the year must be in the interval `[1900,2019]`; The current date mast be greater than the date of birth.
2. Press the "CALCULATE" button to make the computation
3. Age calculator will give the age based on the date of birth and the current date. It also finds how old are we in years, or months, or days, or minutes, or seconds and it points out the number of days till next birthday.

Input : Date format: month/day/year; This component is a calendar interface;
Output : The age in terms of natural numbers.

How to Calculate the Exact Age on a Specified Date?

The age calculator is developed based on the Gregorian calendar (365 days for ordinary year or `366` days for leap year divided by `12` months from January to December).
To calculate exact age from date of birth by using this calculator, we will follow the next steps:

1. Select the month of birth;
2. Select the date of born;
3. Enter the birth year;

There are many algorithms for calculating the exact age and we will present one of them:

1. Start with date as an expression `\text{m/d/y}`, where `m,d` and `y` are three variables for month, day, and year, respectively;
2. If `d\ne1`, find the number of days to the start of the next month and if `d=1`, go to the next step. Depending on the month, this result may be `29-d` days (for February), `30-d` days (for February of leap year), `31-d` days (for `30`-day month), or `32-d` days (for `31`-day month);
3. Find the number of months until New Year's day next year. This may be `12-m`, where $m$ is the current month. In case of `d=1`, the number of months until New Year's day next year is `13-m`;
4. Find the number of years until the start of the next year of the end date;
5. Add on the amount of months and days from the start of the final date year until the entered date.

For example, let us show step-by-step calculation for the date of birth `\text{7/16/2008}` and final date `\text{4/30/2019}`.

1. `m=7`, `d=16` and `y=2008`;
2. Since `d\ne1` and July is a month of `31` days, then the number of days to the start of the next month is `32 − 16 = 16`;
3. The number of months until New Year's day next year is `12-7=5`;
4. Now, from `\text{1/1/2009}` to `\text{1/1/2019}`, there is exactly `10` years.
5. From `\text{1/1/2019}` to `\text{4/30/2019}`, there are `3` months and `29` days. Therefore, we obtain a total count of `10` years, `8` months and `45` days. Note that "30 days" could mean a month or not, depending on the month in context. Since the number of days `45` is greater of `31`, the final result is `10` years, `9` months and `14` days.

The additional details of this calculator also gives us the age in months, days, hours, minutes and seconds. Since one year is `365.25` days, one day is `24` hours, one hour is `60` minutes and one minute is `60` seconds, we can find the exactly age in terms of months, days, hours, minutes and seconds. This means, one year is `365 \times 24+6 = 8,760 + 6 = 8, 766` hours, `8, 766 \times 60` = `525,960` minutes and `525, 960 \times 60` = `31,557,600` seconds.

The above example age calculation shows the complete steps for the date of birth `\text{7/16/2008}` and final date `\text{4/30/2019}` to learn how to find the age manually. For any other date of birth, just supply the date in format `\text{m/d/y}` and click on the "CALCULATE" button. The grade school students may use this age calculator to find how old are they in years, months, days, hours, minutes and seconds and find out how many days there are until their nearest Birthday.

The age calculator and example calculation (work with steps) would be very useful for grade school students (K-12 education) to find the exact age in months, days, hours, minutes and seconds as well as the the number of days till next birthday. It can help us to know how much time we have until the birthday of a friend, spouse or siblings.