When the family FaceTimes with Kevin, it is light outside in both places. At Thanksgiving, however, there is no point during the day when it's light in New Jersey and Vietnam.
When Miguel comes over to the Pearson home for Thanksgiving shortly before Jack dies hes on his cell with Shelley trying to talk to his kids. However this takes place November 1997 and the phone he has is a more recent phone and not something available in the late 1990s.