re dmy tag the tag is used to inform wikipedia bot programs which date format is in use day month year in this case the tag should not be visible to regular viewers and does not directly affect article content some bots may do date updating and maintenance on dates such as removing links or other date formatting therefore a tag ensures the bot will apply the correct date format the other format month day year tends to be associated with american non military articles therefore an tag would help the bots for that case hope this info helps