What time is it? History and typology of time signals from the telegraph to the digital

Time signals provide a sense of “despatialized simultaneity,” a rhythm to the everyday lives of billions of people, and experiences of liveness. This article offers a history of time signals from the 19th to the 21st centuries, identifying three typologies: scheduled time signals, sent mainly by radio and TV; on-demand, such as those of the speaking clock; and automatized, transmitted by the Network Time Protocol for digital devices. The article stresses the importance of time signals in media history and the significance of an infrastructural network of timekeeping/timesharing for the functioning of media themselves.