I was in Diamond City at night and was working on a quest in the city... After leaving a building, the whole entire market area was filled with Christmas decorations and Christmas trees everywhere. I got confused and went to my Pipboy... The date was Christmas Day and the time of the clock was something like 12:04AM... Despite this not making any sense (on how the citizens could put everything up in minutes)... I am rather happy that Bethesda did something like this and can't wait for my game to hit Halloween or other holidays.