The Location’s Time Zone
Enter the location’s Time Zone into the entry box or use the Arrow buttons to select the correct zone.  The Greenwich Mean Time (GMT) is used as a relative standard (London GMT 0,  California - Pacific GMT 8, Thailand GMT -7). For the purposes of this program, hours west of the Prime Meridian are POSITIVE, while those east are NEGATIVE. (12 to -12)
See the manual for suggestions on finding the Time Zone for a new location.