... that it is not 05/21/11, in the American style, but 05/11/21 in the European style, 5 November, 2021.

The proof:
(1) 21 cannot be a month. So it must be a day or a year.
(2) November 21st leaves 05, and November 21, 2005 has already passed.
(3) So 21 must be the year.
(4) It can't be May 11, 2021, since May 11th was Salvador Dali's birthday. Enough said.
(5) God is a mathematician, and would not use any date as disorderly as Month, Day, Year ~ it will certainly either be from longer period to shorter or shorter period to longer. Since in the end time, the time will come when the year is redundant, clearly it will be shorter period to longer so that in the last year, the year can be dispensed with.

Ergo, 5/11/21, 5 November, 2021, qed


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.