in code_samples/tool_window/src/main/java/org/intellij/sdk/toolWindow/CalendarToolWindowFactory.java [87:91]
private String getTimeZone(Calendar calendar) {
long gmtOffset = calendar.get(Calendar.ZONE_OFFSET); // offset from GMT in milliseconds
String gmtOffsetString = String.valueOf(gmtOffset / 3600000);
return (gmtOffset > 0) ? "GMT + " + gmtOffsetString : "GMT - " + gmtOffsetString;
}