DateTime is nothing new, but it's definitely under-used by many. It was made available in PHP 5.2.0 but got some of its best features until PHP 5.3.0. PHP 5.3.0 is pretty old now, but I learned about DateFormat::createFromFormat() after reading a new addition to PHP The Right Way: Date and Time.

He shares to "offender" examples where using this function allowed him to simplify and reduce the amount of code needed to handle the formatting of a date into a MySQL format and calculating the difference between two time values.