Many physiological processes have circadian rhythms driven by a biological clock in the suprachiasmatic nuclei (SCN) of the brain. Within the SCN, some neurons express the molecular components of the clock and others do not. Exactly how the clock mechanism is coupled to neuronal activity is not precisely understood. Investigation of the electrophysiological properties of SCN neurons by Belle et al. found that, contrary to the conventionally expected rapid firing rate of the cells during the day, clock-containing cells tended not to fire despite being in an electrically excited state. Modeling and experimental characterization of changes in channel activity revealed unexpected electrophysiological properties of the SCN cells requiring a reassessment of how the circadian clock regulates activity of SCN neurons.