The corpus callosum, a major white matter region central to cognitive function, is vulnerable to aging. Using zeitgeber time (ZT) aligned with environmental light/dark cycles, we investigated temporal gene expression patterns in the corpus callosum of young (5-month-old) and aged (24-month-old) mice using RNA-seq. Comparative analysis revealed more differentially expressed genes across ZT pairs in young mice than aged mice. In addition, complement pathway genes, including