answer: #Person1# tells #Person2# #Person2# can set the clock forward for daylight to save time and it's due to their position on the planet and the rotation of the earth. #Person2# then understands the time difference.
documents: #Person1#: Did you set your clock forward for daylight savings time?
  #Person2#: What? Why do we have to do that?
  #Person1#: Well, at the start of the spring we usually have more daylight in the mornings and less in the afternoon. This is basically due to our position on the planet and the rotation of the earth. In any case, to take better advantage of the daylight available, we compensate by moving our clocks forward one hour.
  #Person2#: I see. That's convenient! I never understood things like this, such as GMT. I never know what time zone we are in or when to change my clock!
  #Person1#: That just stands for Greenwich Mean Time. Here in California, we are in Pacific Standard Time, that is eight time zones west of Greenwich. Remember when we were in Beijing? Well, then we were in China Standard Time, and that's eight time zones east of Greenwich!
  #Person2#: That's why it was so weird traveling from Beijing to LA! Because of the huge time difference, even though we left Beijing at noon and flew for more than eight hours, we still arrived in LA the same day at noon! It's like we went back in time!