检索时，存储在数据库中的Hibernate Timestamp值为零

What i want to do is to get the difference between two events, in this case the event when a store starts to fabricate certain item and the time when the same store starts to transport it to the customers location. Im using java and hibernate to develop this WebApp. the entity is called Report ( as i will generate a report from this information) the attributes for both events are:What i want to do is to get the difference betw