My LT says January....
but I remembered this discussion from last year and just went back to review it (search for "service selection results" and don't forget to set it to go back a full year) so here goes...
SEALs find out first...in last year's case: Dec 14th
Everyone else seems to have found out starting on Dec 22nd
Apparently Big Navy tries to get them out before Christmas but there are no guarantees. Also, this is pretty deep into the Christmas season so there are typically problems disseminating the information (i.e. middies on break, staff on leave, etc.) so make sure your LT has good contact info.
Luckily, I hear they're still hurting for NFOs as that is my #1 choice.
Best of luck to y'all and Merry Christmas!!!