Can anyone find any other date (anniversary date, target date) in their account?
I can't - so I really do think that this is everyone*'s "anniversary date" which forms the basis of the membership year.
Does anyone have anything in their account that shows otherwise? Tier Credits from flights in the past weeks/months? Some indication of a date that they recognise from the old GC days, or a date other than November 21st?
*[Everyone who was "ported" from GC. Genuine new joiners will obviously have new dates corresponding to the day they signed up...and as today was the first day to do this, that would be 1 December and onwards]