"The hours of folly are measured by the clock; but of wisdom, no clock can measure."
William Blake, poet
Clocks usually have two jobs. One is to display the right time; the other is to give a measurement of a time interval. Digital clocks are numeric. Hours, minutes, and seconds are represented by numbers and the display can be made small and linear. Although German inventor Josef Pallweber patented a digital watch as early as 1883, the development of the digital clock proper is closely associated with the history of digital displays. The earliest examples of these were the glowing end of valve tubes that could indicate numbers. These were much loved by the nuclear physics instrumentation industry in the 1950s.
The modern digital clock relied significantly on the development of the light emitting diode (LED) and liquid crystal display (LCD). The first commercially usable LEDs were developed in the 1960s, and the first active matrix LCD panel was produced in 1972. Film director Stanley Kubrick famously showed a futuristic digital clock in his 1968 science fiction masterpiece, 2001: A Space Odyssey.
A problem with digital alarm clocks is that they flash to a default setting when switched off and can fail to alarm after a power surge or outage. Small and cheap digital clocks have been used in many other devices from microwave ovens to cell phones. While digital watches were very popular in the 1980s, the analogue display is arguably more fashionable again today.
