Originally, the date was said “April the 22nd” just like Americans do. But then the year went first (when needed). Nothing wrong with 2009/4/22. The problem is that Americans swapped only half of the date, putting the year last, ie 4/22/2009. Which is obviously confusing for the rest of the world who write it as 22/4/2009. Both systems are logical if they are consistent, it’s the inconsistency of the American system that makes it confusing.
Also, in the arabic numerals, numbers are written from left-to-right, which for them is backwards (since they write right-to-left). We kept their order for the numbers, even though we write in the opposite direction. After a while, our “four and twenty” (which should have been written 42) became “twenty four” (written 24). Germans still say the old numbers, yet write them backwards.
(ok I know this was confusing, but it will make sense if you try it out)
My mum has an old degree which starts something like “in the year of the Lord Seventh and Sixtieth and NineHundredth and Thousandth, on the Sixth Month, on the Third and Twentieth Day”. All it means is that she graduated on 23/6/67.