24-hour analog dial

Clocks and watches with a 24-hour analog dial have an hour hand that makes one complete revolution—360°—in a full day, or 24 hours per revolution. In contrast, the more familiar 12-hour analog dial has an hour hand that completes two revolutions per day, or 12 hours per revolution.

Twenty-four-hour analog clocks and watches are commonly used by logistics workers, firefighters, police officers, paramedics, nurses, pilots, scientists, and military personnel. They are often preferred because they present an unambiguous representation of the entire day at once. This definition specifically refers to the use of a full circular dial to represent a 24-hour cycle. Simply using numbers from 0 to 23 (or 1 to 24) is known as the 24-hour clock system.

Sundials also use 24-hour analog dials, as the shadow follows a path that repeats approximately once per day. Many sundials are marked with the double-XII (or double-12) system, where the numbers I to XII (or 1 to 12) appear twice—once for the morning and once for the afternoon and evening. Thus, VI (6) appears twice on many sundial dials: once near sunrise and once near sunset.

Modern 24-hour analog dials—aside from sundials—are almost always marked with 24 numbers or hour markers around the edge, following the 24-hour clock system. Because they display the entire day in one rotation, they do not require AM or PM indicators.