Well, this type of thing used to happen all the time and there are a bunch of famous examples. When communications technology consisted of a person carrying a letter the word got around more slowly. The battle of New Orleans in the war of 1812 occurred after the war formally ended for example.

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again. Alternatively, questions of this type can be directed to more appropriate subreddits, such as /r/history or /r/askhistory.