Mongolia has two time zones. Mongolian central time is 7 hours ahead of GMT year round, which is the same as all of China. As of 2007 the Mongolian government decided to discontinue adjusting time 1h for daylight saving in the summer period.
 
China has one large time zone, so Beijing, although in a more easterly location than Ulaanbaatar, is also 7 hours ahead of GMT.  Russia has eleven time zones, and the time by which the Trans Siberian Railway operates is Moscow time (+3 hrs GMT) all through.