the influence of the Italian timekeeping system, which started counting the hours of the day at sunset or twilight. In northern Europe, the double XII system was gradually superseded during the 14th and 15th centuries by the single XII (12-hour system), leading to the widespread adoption of the 12-hour dial for popular use. The 24-hour analog dial continued to be used, but primarily by technicians, astronomers, scientists, and clockmakers. John Harrison, Thomas Tompion, and Mudge built a number of clocks with 24-hour analog dials, particularly when building astronomical and nautical instruments. 24-hour dials were also used on sidereal clocks. The famous Big Ben clock in London has a 24-hour dial as part of the mechanism, although it is not visible from the outside. In the 20th century, the 24-hour analog dial was adopted by radio amateurs, pilots, submariners, and for military use. Today 24-hour analog watches and clocks are still being manufactured today, and are sought after by collectors and enthusiasts. Manufacturers who make 24-hour analog watches include Glycine, Raketa, Vostok, Fortis, Poljot, Swatch, and many others. Design The major variation in the design of 24-hour analog dials is the location of midnight and noon. Although always opposite each other, 180° apart, noon is sometimes at the top, sometimes at the bottom. A few rare variants place noon and midnight at the right and left sides. There is no ambiguity if the 24-hour numbering is used. In the United States, the government and military commonly use 24-hour clocks having noon at the bottom; the variant with noon at the top is far less common. Watches A 24-hour watch is a type of watch with an hour hand that completes a revolution every 24 hours. The face may be arranged in either of two ways: with noon at the top and midnight at the bottom (similar to how one might observe the passage of the Sun over their time zone whilst facing south), or else rotated 180° with midnight at the top and noon at the bottom (as pictured). Multiple time zones can be displayed by having multiple hour hands or a rotating bezel. The bezel is a ring around the outside of the watch's face. When it is used, the top of the watch always represents midnight (or noon) GMT. The bezel, which also has hour markings, is then rotated so that its numbering represents local time. So, a pilot