That’s locality of reference, though, similar to how you can say “here” or “there” for spatial coordinates. Everybody is aware of the year and month, so you omit it as given. The order of significance is still year, month, day.
Imagine if a harried time traveler jumped out of their time machine and asked you the date. Would it make sense to say, “Why, it’s the 1st.” (Or more possible, if a friend awoke from a coma.) If you ask somebody when they were born, most people will give the year at minimum. Of course, there are some weirdos out there, and you recognize them when you ask when they were born, and they say, “on a Tuesday.” Same for the date of the Norman invasion of Great Britain. If you don’t already have some sense of history, then knowing it happened about the 20th isn’t very edifying.
That’s locality of reference, though, similar to how you can say “here” or “there” for spatial coordinates. Everybody is aware of the year and month, so you omit it as given. The order of significance is still year, month, day.
Imagine if a harried time traveler jumped out of their time machine and asked you the date. Would it make sense to say, “Why, it’s the 1st.” (Or more possible, if a friend awoke from a coma.) If you ask somebody when they were born, most people will give the year at minimum. Of course, there are some weirdos out there, and you recognize them when you ask when they were born, and they say, “on a Tuesday.” Same for the date of the Norman invasion of Great Britain. If you don’t already have some sense of history, then knowing it happened about the 20th isn’t very edifying.