The study investigates the physiological significance of peripheral tissue circadian clocks, focusing on the liver. Mice with a liver-specific deletion of Bmal1, an essential clock component, exhibit hypoglycemia restricted to the fasting phase of the daily feeding cycle, exaggerated glucose clearance, and loss of rhythmic expression of hepatic glucose regulatory genes. These findings suggest that the liver clock contributes to homeostasis by driving a daily rhythm of hepatic glucose export that counterbalances the daily cycle of glucose ingestion resulting from the fasting-feeding cycle. The study provides direct evidence that a peripheral tissue circadian clock has a significant physiological function in vivo, highlighting the importance of peripheral clocks in metabolic regulation.The study investigates the physiological significance of peripheral tissue circadian clocks, focusing on the liver. Mice with a liver-specific deletion of Bmal1, an essential clock component, exhibit hypoglycemia restricted to the fasting phase of the daily feeding cycle, exaggerated glucose clearance, and loss of rhythmic expression of hepatic glucose regulatory genes. These findings suggest that the liver clock contributes to homeostasis by driving a daily rhythm of hepatic glucose export that counterbalances the daily cycle of glucose ingestion resulting from the fasting-feeding cycle. The study provides direct evidence that a peripheral tissue circadian clock has a significant physiological function in vivo, highlighting the importance of peripheral clocks in metabolic regulation.