Types of Clocks

Clocks can be classified by the type of time display, as well as by the method of timekeeping.

Time display methods

Analog clocks

A linear clock at London's Piccadilly Circus tube station. The 24 hour band moves across the static map, keeping pace with the apparent movement of the sun above ground, and a pointer fixed on London points to the current time

Analog clocks usually indicate time using angles. The most common clock faceuses a fixed numbered dial or dials and moving hand or hands. It usually has a circular scale of 12 hours, which can also serve as a scale of 60 minutes, and 60 secondsif the clock has a second hand. Many other styles and designs have been used throughout the years, including dials divided into 6, 8, 10, and 24 hours. The only other widely used clock face today is the 24 hour analog dial, because of the use of 24 hour timein militaryorganizations and timetables

Another type of analog clock is the sundial, which tracks the sun continuously, registering the time by the shadow position of its gnomon. Sundials use some or part of the 24 hour analog dial. There also exist clocks which use a digital display despite having an analog mechanism—these are commonly referred to as flip clocks.

Digital clocks

Digital clock outside Kanazawa Station displaying the time by controlling valves on a fountain

Digital clocks display a numeric representation of time. Two numeric display formats are commonly used on digitalclocks:

• the 24-hour notationwith hours ranging 00–23;
• the 12-hour notationwith AM/PM indicator, with hours indicated as 12AM, followed by 1AM–11AM, followed by 12PM, followed by 1PM–11PM (a notation mostly used in the United States).

Most digital clocks use an LCD, LED, or VFDdisplay; many other display technologies are used as well (cathode ray tubes, nixie tubes, etc.). After a reset, battery change or power failure, digital clocks without a backup batteryor capacitoreither start counting from 00:00, or stay at 00:00, often with blinking digits indicating that time needs to be set. Some newer clocks will actually reset themselves based on radio or Internet time servers that are tuned to national atomic clocks. Since the release of digital clocks in the mainstream, the use of analogue clocks has dropped dramatically.

Auditory clocks