In this review, we will address the role of the circadian clock in the development and progression of both common and rare neurodegenerative diseases - specifically in AD, Lewy body dementia (LBD), PD, Huntington’s disease (HD), progressive supranuclear palsy (PSP), Pick’s disease (PiD), and frontotemporal lobar degeneration-tau (FTLD-tau). The gene discussed is CLOCK; the disease is Parkinson disease.