The UTC offset (offset from Coordinated Universal Time ±) is the difference in hours and minutes from Coordinated Universal Time (UTC) for a particular place and date. The local civil time in a time zone which observes UTC+8 is calculated by adding 8 hours to UTC.
± Another name for GMT (Greenwich Mean Time , at 0° longitude, from which all time zones are calculated)
Time zones and time offsets
A time zone is a geographical region where just about everybody observes the same standard time.
A time offset is an amount of time subtracted from or added to UTC to get the current civil time - whether it's standard time or Daylight saving time.
In any particular time zone residents either observe standard time all year round (as in Hawaii or most of Arizona) OR they observe standard time in winter and daylight time in summer.
Daylight saving time
Several regions in North America, Europe and Australia use daylight saving time (DST). The UTC offset during observation of DST is typically obtained by adding one hour to standard time. Central European Time UTC+01:00 is replaced by Central European Summer Time UTC+02:00, and Pacific Standard Time UTC−08:00 is replaced by Pacific Daylight Time UTC−07:00.
+List of UTC time offsets