Date of Birth Calculator | Birthday Calculator

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Usually, the age of a person is calculated from the date of birth of the person to the current date. But what does one do when they want to find out the date of birth itself?

Date of Birth Calculator | Birthday Calculator

This is why we have this calculator for you. All you need to know is your current age and the date of the day. A person’s age and date of birth can be calculated differently in different cultures keeping in mind their social practices and norms. Usually a person adds on another year to their age on their date of birth every year. For example of a person who has lived for 18 years will become 19 on the date of his birth in the coming year.

In this article we will learn

  • 1. How to calculate date of birth
  • 2. How many days until my birthday

How to Calculate date of Birth | Birthday

To do this manually, you would need to know your exact current age and the date of the day when you’re calculating it from. Then you can simple subtract the number of years from the current year, number of days and you will have found out your date of birth.

Example 1: A is 32 years and 12 days old on 12 January 2021. When would be his birthday?

First we would subtract 32 from 2021
We will get 1989
Now we subtract 12 days from 12 January 1989
We get 1 January 1989
A ‘s date of birth is 1 January 1989

Example 2: B is 27 years and 2 months 1 day old on 8 January 2021. When would be their birthday?

First we would subtract 2021 and 27
We will get 1993
Now we subtract 2 month and 1 day from 8 January
We get November 7th
Hence the date of birth will be November 7 1993

In some cultures, age or date of birth is expressed by counting years sometimes with or without including the current year. For example, a person who is 20 right now is also in their 21st year of their life.

In one of the many traditional Chinese age systems, people believe that they are born at the age of 1 and another year is added to their age not on their birthdays but on the Traditional Chinese New Year. For example, if one baby was born just 3 days before the Traditional Chinese New Year, 3 days later the baby will turn 2 even though they are just 3 days old.

In some situations, calculating the birth date can become confusing especially when the dates are at the opposite ends of the month. For example, when we calculate the birth date of a person who is 12 years and 9 months at the end of February 21th , calculating the birth date becomes difficult since we will now have to consider 21 to 21 as one month. Although there are different ways to calculate the birth date.

How many days until my birthday?

To find this we will first find the date of birth by subtracting the current age from the current year. Then we will count the months till when the date occurs again.

Example: R is 20 years 4 months old in may 3 2020. How many days are there until their next birthday?

First we subtract 20 from 2020
We get 2000
Now we subtract 4 months from may
We get January 3
Hence we now know that R’s birth date is 3 January 2000

Their next birthday will be on 3 January 2021 which is 9 months away


While every effort has been done in developing this calculator, we are not accountable for any incidental or consequential damages arising from the use of the calculator tools on our web site. These tools serve to visitors as a free calculator tool. Please use at your own risk. The calculations provided are just a guide. You are advised to speak to a professional financial advisor before taking any financial decision.