Syntax

use Symfony\Component\Validator\Constraints as Assert;
 
class Event
{
    /** @Assert\DateTime() */
    private $startDate;
 
    /**
     * @Assert\DateTime()
     * @Assert\Expression("value > this.startDate")
     */
    private $endDate;
 
    // ...
}

In Symfony 4.0 a new propertyPath option was added:

use Symfony\Component\Validator\Constraints as Assert;
 
class Event
{
    /** @Assert\DateTime() */
    private $startDate;
 
    /**
     * @Assert\DateTime()
     * @Assert\GreaterThan(propertyPath="startDate")
     */
    private $endDate;
 
    // ...
}