What is the data type of your MySQL column? If it's the DATETIME type, there are LOTS of mysql functions you can use in your SQL query to format the date however you want.
If it's an integer, then using arithmetic operations will probably be faster and more efficient than using the substr() method posted above. If it's a string, then you're more or less stuck slicing up the string.
You can do this using substr() as above or using a regular expression matching function, like preg_match().
// year month day hour minute second
$matches is an array that will contain all the matched strings.
$matches will be the entire original string.
$matches will be the year,
$matches will be the month,
... and so on.