# [SOLVED] Calculating birthdate by given age

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I already have a method of calculating the age by a given birthdate, but I have no idea how to do that in reverse. Here's my method on calculating the age by given birthdate:

```<?php
function calculate_age(\$month, \$day, \$year) {
global \$month, \$day, \$year;
\$time = time();
\$new_date = mktime(0, 0, 0, \$month, \$day, \$year);
\$age = (\$new_date < 0) ? (\$time + (\$new_date * -1)) : \$time - \$new_date;
\$year = 60 * 60 * 24 * 365;
\$return_age = \$age / \$year;

return floor(\$return_age);
}
?>
```

But my question is how do you reverse this process so it outputs the birthdate?

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If im getting it right, u have the age of a person (ie. 20) and by that u want to calculate his birthdate (normaly only year). If so then consider the following:

```<?php
\$age = '20';
echo date('Y', strtotime("-\$age years")); //it will echo 1987
?>
```

Ok, thanks.

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If all you have is the age in years then the year of birth is as close as you'll get

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