This is the second month in a row that my report shows changes on the same date.
This event is generated when DC change password for Trust Relationship, attribute trustAuthInfo.
You can verify which attribute have been modified using adsiedit tool. On system container open properities of trusteddomain object and check this attribute (msDS-ReplAttributeMetaData). You can see with attribute have been modified at event time. If attribute is trustauthinfo then is password change of relationship.