$setGMTOffset tells the runtime system the difference in seconds between Greenwich Mean Time (GMT) and local time. This difference is positive for time zones west of Greenwich and negative for zones east of Greenwich. The value of the GMT offset may be examined by $getGMTOffset or by the MAINEX subcommand GMTOFFSET. MAINSAIL's time-zone-related facilities are described in more detail in Section 24.2 and in the description of MAINEX in Chapter 21 of the MAINSAIL Utilities User's Guide.
After a call to $setGMTOffset, $timeSubcommandsSet becomes TRUE.