Each timezone is described by a file that is kept in the /etc/zoneinfo directory on the filer. The name argument is actually the name of the file under /etc/zoneinfo that describes the timezone to use. For instance, the name "US/Pacific" refers to the timezone file /etc/zoneinfo/US/Pacific. These files are in standard ``Arthur Olson'' timezone file format, as used on many flavors of UNIX (SunOS 4.x and later, 4.4BSD, System V Release 4 and later, and others).
GMT+13 is to allow DST for timezone GMT+12.