Dual Time Zone (or GMT)

The terms dual time and GMT are often used interchangeably because they share the same purpose — to display the time in two different time zones simultaneously. There is, however, a slight distinction. A GMT watch displays a time zone using a 24-hour index that can be used to determine if it’s day or night in that location. A dual-time zone watch uses a 12-hour index, often paired with a day/night indicator.