In your Entity you must import the namespace:
use PUGX\ExtraValidatorBundle\Validator\Constraints as ExtraAssert;
After that you can use DateRangeValidator just writing relevant assert in annotation of your property:
/**
* @ExtraAssert\MaxDate(limit="+2 years")
*/
protected $date;
Limit option must be compliant to php documentation: Supported php Date and Time Formats