This question is commonly asked among people in the equine community. Eventing, or Three Day Eventing is said to be the ultimate test of horse and rider. In fact, this grueling event was used as a test for cavalry horses. Though it has been modified since then it is still extremely difficult for the horse and rider. True to it's name the event takes place over the course of three days. Each day the horse and rider must complete a different task, testing the full range of equestrian skills.