Zeitgeber (from German for "time giver", synchronizer) is any external (exogenous) cue that entrains the internal (endogenous) time-keeping system of organisms. The strongest zeitgeber, for both plants and animals, is light. Other, non-photic, zeitgebers include temperature, social interactions, pharmacological manipulation and eating/drinking patterns.

The German term „Zeitgeber“ came into the English language when Jürgen Aschoff, one of the founders of the field of chronobiology, used it in the 1960s. It is now in common use in the scientific literature in this field.

See also

• Phase response curve
• Circadian rhythm
• Infradian rhythm
• Ultradian
• Melatonin
• Suprachiasmatic nucleus or nuclei (SCN)

Literature

• Aschoff J (1965) The phase-angle difference in circadian periodicity.In "Circadian Clocks" (J. Aschoff, ed.). North Holland Press, Amsterdam, p 262–278.

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