thank you to whomever re-organized the spreadsheet.
it is now pretty clear the strongest determinant for JS2's is not JS1 date but rather JS1 invitation date.
all the November JS2's had, for the most part, October JS1 invites, while all the December JS2's had, for the most part, November JS1 invites. If that's the sequence, then it explains in part why so many folks with December JS1 invites have not heard back yet.
If that pattern plays out, it means that the folks with December JS1 invites, assuming they didn't schedule their interviews too late, will hear back at the end of January, given that JS2's came out at the end of Nov/Dec right before the school holidays.
If you want to get even more exact, you could speculate that, given that Jan 20 is MLK day and the school is off, JS2's might come about right around then, maybe the Thursday or Friday before that. Or they might just come at the very end of January. I don't know.