Question

The following code outputs 1970-01-01 which is wrong.

<?php
$dob='17 Jan 1900';
$datetime = strtotime($dob);
$dob = date("Y-m-d", $datetime);
echo $dob;
?>

However it works fine with $dob = '17 Jan 2000';

Answer 1

If your PHP version allow it consider Using DateTime instead of strtotime :

$date = DateTime::createFromFormat('d M Y','17 Jan 1900');
echo $date->format('Y-m-d');

For PHP version between >= 5.2 and <= 5.3 simply use the DateTime constructor :

$date = new DateTime('17 Jan 1900');
echo $date->format('Y-m-d');