The brain clock, located in the suprachiasmatic nucleus (SCN) of the hypothalamus receives direct retinal input providing the entire body with an internal representation of external solar time. The pathways by which this small nucleus signals so broadly involve co-occurring nervous and diffusible output signals, though the latter are less understood. Portal pathways, such as the well-known pituitary portal pathway, provide a mechanism whereby signals of neural origin can reach local, specialized targets without suffering dilution in the systemic blood supply. The newly discovered pathways involve direct connections between each of the sensory circumventricular nuclei at their point of their attachment to the brain. These nuclei line the brain’s ventricles, and their leaky blood vessels and large perivascular spaces represent a route whereby secretions from the SCN can be relayed and then amplified, providing a pathway to achieve global coordination of circadian clock signaling. This review provides a narrative that incorporates our understanding of SCN neural and diffusible output signals, with particular emphasis on the contribution of brain fluid compartments and the fluids therein.