Honestly, reading that scenario it is hard to say who abruptly changed plans. One sets a time, then abuses that agreement, but then gets upset that the second one behaves the same. If it is a “special occasion”, one does not “set a time because one has errands to do before”, and then fail to plan ahead to be on time. That sends a message that it was not so special to begin with. This relationship involves two inconsiderate people.