I definitely had more than 3 hour of time difference between, minus 2 hours, 1 hour at least!
And I would expect that the game uses the local time of the player to calcualte the mission time.
If not then I would call it a bad mission design and I won't play these sort of missions again, as well as many other players I guess.
You don't seem to understand the concept of UTC, that is not ED's problem. I am on UTC-7 and have no problems with the mission times.