A large variety of devices have been invented to measure time. The study of these devices is called Horology. Here is a brief list of a few of the most popular:
- The most common devices in day-to-day life are the clock for periods less than a day and the calendar for periods longer than a day.
- Clocks can range from Watches, to more exotic varieties such as the Clock of the Long Now.
- Clocks can be driven by a variety of means, including a pendulum.
- There are also a variety of different calendars, for example the Lunar calendar and the Solar calendar, although the Gregorian calendar is the most commonly used.
- A chronometer is a timekeeper precise enough to be used as a portable time standard, usually in order to determine longitude by means of celestial navigation.
- The most accurate type of measuring devices for time are atomic clocks.
- More archaic devices include the Hourglass, the Sundial, the Tempometer and the Water clock.