In the USA September 11 is 9/11. Since 911 is the number for emergencies this makes sense.
Using European style, it's 11/9 And If you start the Jewish Months from Tishrei, then Tisha b'Av is also a kind of 11/9 -- I.E. Av the 11th month; 9 the 9th day
In general. I wonder out loud, why don't we Observe the Hebrew Date, namely 23 Elul?
Full disclosure: my old shul observed Krystallnacht on the Secular Date, too, but Breuer's used the Hebrew Date, 15 Marcheshvan iirc.