Internal clock may refer to:
Circadian clock, a biochemical mechanism that oscillates with a period of 24 hours (in accordance with the day-night cycle); driver of the circadian rhythm de Broglie internal clock, hypothetical clock in an electron, constituting part of the mechanism by which a pilot wave guides a particle Electronic oscillator, an electronic circuit that produces a periodic, oscillating signal, often a sine wave or a square wave
See also Clock rate, the frequency of an electronic oscillator (such as an oscillator crystal) used by computer processor Proper time, the elapsed time between two events as measured by a clock that passes through both events