I just use d for division, as it is the same for all leagues.
The last skill squish happened on 11 October. My main account in k2 got squished -40 points, my alt account in k3 got squished -4 points. That was about signup day for this new season. You can see this in your swgoh.gg profile page.
People would have been promoted/demoted leagues on the day that the end of last season rewards were handed out.
Any divisional movement due to skill squish happens after match 1 of the new season. It can sometimes be canceled out by a win on that first match, so people often don't notice they were squished at all. But a d1 person is moved the most by the formula, so it can be a higher squish than the win is worth.
The other thing that can affect the league promotion maelstrom, is that a k5 player may have a skill rating that actually fits anywhere at all in the aurodium league. You don't get moved to a1, you get moved to aurodium league, then wherever your actual skill rating sits you in it. Then at the start of the new season there will be some squish applied as well, possibly bumping divisions as well, but only actually moving after the first match.