Day of month has no meaning without specifying the month, unless you specifically say “this month”. So providing the day before the month does not provide any

Day of month has no meaning without specifying the month, unless you specifically say “this month”. So providing the day before the month does not provide any contextual advantage. However, in most cases, the year is not necessary for contextual meaning. So the alternatives are month + day or month + day and year. If you don’t understand why something is done, but it’s been done for a long time, chances are that it evolved to be that way for a reason. If something is arbitrarily dictated to replace an evolved system, there is most likely some information or practical purpose that is lost.