Through December 2.
I finally got back a shipment of cards I'd mailed in late September of last year, that's 13+ months. (It spent two months in QA1 and suspiciously had a factory stamped card come back with an MK qualifier.) If that's typical, I'm guessing my late December order will be at least March 2022, which is 14+ months.
If they keep at the apparent rate, it wouldn't surprise me if they were on pace to clear out the backlog by next August-ish. I really hope I'm way overshooting the mark on that.