Eastern Time Zone. You are correct that the Dow futures were down substantially before midnight EDT. They were down about 700 points until Trump ran the table with Florida, Ohio, and North Carolina. When Pennsylvania was called from Trump, the futures began their turnaround, before the “blue wall” for Hillary! collapsed. By 2:30 am, when Fox and a few other networks began saying a Trump victory was likely, the futures were in a steep rise, turning dramatically positive.
Yes, it was the uncertainty, not the prospect of Trump winning that were causing them to drop - they thought maybe the election would be undecided and drug out, but it didn’t end up being even close.