## How to calculate age from the date of birth?

First of all to **calculate age** we need the exact date of your birthday and today's date (time also if need a detailed difference). Today is 01/21/2017 and the exact time is 23 hours 31 minutes and 50 seconds.

Note: If you just want to calculate age and do not care about the calculation details and do not want to read our age calculation formula explanation, please visit our site's **age calculator** tool by clicking on the age calculator menu item.

The formula for calculating the **time difference** between the two dates is a simple subtraction and as with all subtractions we start from the most right unit.

### For a detailed age calculation you will have to do these steps:

- dates should be displayed in year/month/day hours:minutes:seconds format
- calculate the seconds difference between now and the birth date
- subtract the birth date minutes from the now minutes
- determine the difference between the birth and now hours
- get the number of days by subtracting the birthday days form today's date
- calculate the months difference between two dates
- finally determine the year difference, which should be the easiest

### Calculating age (elapsed time between two dates) rules:

- if you have insufficient units, borrow one from the leftward unit
- a borrowed unit should be also subtracted from the adequate place

## How to calculate age at a given date?

To calculate age between a birth date and a given date is the same as calculating age between today's date and the birth date. The only difference here is that we need to use the given date instead of today's date. Simply follow the steps described above to get the difference between two dates.

If you wish to find a date for a given age, instead of subtraction use addition and the result will be the wanted date.

### Age calculation example:

- birth date: 1979/08/26 09:45:00
- now date: 2010/10/12 10:03:44

The seconds difference is 44 (44 - 00 = 44), while we need to borrow one hour to calculate the minutes. Now 03 + 60 = 63, so 63 - 45 = 18 minutes. Because we borrowed on hour, the now date's hours unit will change from 10 to 09 and the difference between 09 and 09 is zero.

Borrowing one month from the leftward unit, we get 17 days (31 - 26 = 05 from August and 12 days from October). Subtracting 01 borrowed month and 08 birth date months from 10 months will produce 01 month difference and the years difference will be 31 (2010 - 1979 = 31) years.