All day and night; all of the time.

An extremely accurate reference clock whose operation is based on an atomic process, typically the frequency of electromagnetic radiation associated with a specified energy-level transition in an element such as cesium.

(Britain) A single stem of a dandelion in its post-flowering state with the downy covering of its head intact. The term is applied when the flower is used, or is thought of as suitable for use, in a children's pastime by which the number of puffs needed to blow the filamentous achenes from a dandelion is supposed to tell the time.

continuous; incessant; without interruption; all day long, 24 hours per day; nonstop: from the concept that it happens while the hands of the clock go all the way around.

(informal) A telephone service where a pre-recorded message gives the correct time.

Any clock that uses a pendulum to regulate its movement

(idiomatic, almost always preceded by the and often followed by for) Time is running out; a deadline is approaching.

plural of chess clock

A marine chronometer.

plural of light clock