GMT, or Greenwich Mean Time, is a time standard that refers to the mean solar time at the Royal Observatory in Greenwich, London. In watchmaking, GMT watches are designed to display multiple time zones simultaneously, making them particularly useful for travelers and professionals who need to track time across different regions. A GMT watch typically features an additional hour hand that completes a full rotation every 24 hours, pointing to a 24-hour scale on the bezel or dial. This allows the wearer to read a second time zone at a glance. The 24-hour scale helps distinguish between day and night in the second time zone, which is crucial for accurate timekeeping. GMT watches often include a rotating bezel that can be adjusted to track a third time zone, enhancing their functionality. The concept of GMT in horology is rooted in the historical need for a standardized time reference for navigation and global communication. Today, GMT watches are prized for their practicality and are a staple in the collections of many watch enthusiasts. They combine technical precision with aesthetic appeal, often featuring robust designs suitable for both professional and casual settings.