Early research on the cyanobacterial clock focused on characterizing the genes needed to keep, entrain, and convey time within the cell. As the scope of assays used in molecular genetics has expanded to capture systems-level properties (e.g., RNA-seq, ChIP-seq, metabolomics, high-throughput screening of genetic variants), so has our understanding of how the clock fits within and influences a broader cellular context. Here we review the work that has established a global perspective of the clock, with a focus on (a) an emerging network-centric view of clock architecture, (b) mechanistic insights into how temporal and environmental cues are transmitted and integrated within this network, (c) the systematic alteration of gene expression and cellular metabolism by the clock, and (d) insights into the evolution of temporal control in cyanobacteria. Expected final online publication date for the Annual Review of Genetics Volume 49 is November 23, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.