You can check your time zone in directory: $(GNUSTEP_ROOT)/System/Libraries/Libraries/Resources/gnustep-base/NSTimeZones/zones/. For example, eastern Ameirca should be in the time zone of American/New_York. You can also calculate your GMT+/-.

Use defaults to change the time zone:

  
  defaults write NSGlobalDomain "Local Time Zone" "America/New_York"
  
  

Check your ~/GNUstep/Defaults/.GNUstepDefaults. There should be:

  NSGlobalDomain = {
    "Local Time Zone" = America/New_York;
  };
  

Or you can use this command to read the user defaults:

  
  defaults read NSGlobalDomain "Local Time Zone"