Yes, I know there are more 'mirror dates' to come if you use European date styling (DD/MM/YY), but the Plan originated in the States, so I'm sticking with US date styling (MM/DD/YY).
By the way, this is NOT datefagging. I am not suggesting that anything will happen today. I'm just pointing out a bit of trivia for those who like numbers, etc.
Edit: As Vicarious points out below, today (the day after the winter solstice) is when the days start getting longer (more light). So, leading up until today, the days have been getting darker, but is today the day when things (almost imperceptibly) start getting brighter?
Correction and two Challenges: Today is not the last mirror date (this century). Depending on date formats, you could see one as soon as six weeks from now (2/2/22). Someone mentioned the pattern '03/11/30', '04/11/40', etc (which also works with any single-digit day in the middle). With long-form dates, you can get 09/02/2090 (or 2090/09/02). But, (and here's the first challenge), is today the last mirror date (this century) that is the day after a winter solstice (Dark to Light)? And, (second challenge), is there any mirror date (this century) after 09/11/90? (If not, the last mirror date occurs on an anniversary of 9/11)
Wait...what? We only need to wait six weeks for the next mirror?
Yep, I guess I was fixated on the 'symmetry' of the 'first and last' numbers being equal sizes (the '12' and '21'). If you ignore the hyphens, yours works.
Incidentally, if you use YYYY/MM/DD date styling, the last mirror date this century is 2090-09-02. (We will almost certainly have arrests by then. /s)