Is it Seven of Nine day? 7th day of the 9th month? Might depend which calendar we use, American or European calendar? The other option would be ninth of July?
i don't think the calendar system/order matters. seven of nine is one smaller unit of a larger collective. it logically follows that a day is a smaller unit of a larger collective of days, a month. thus it could only be the seventh day [smaller unit] of the ninth month [larger collective].
September 7 makes more sense. Let's all wear really tight outfits and use words like irrelevant and inefficient as much as possible!