From the late 1960s onwards, artist Hanne Darboven (1941, Munich – 2009, Hamburg) adopted a daily practice of writing (Schreibzeit). Through a vast body of works that took many forms – including calendars, musical scores and books – she spatialised and visualised time. Ein Jahrhundert-ABC (1970–71) is composed of nineteen panels each containing forty-two sheets of paper, each marked according to Darboven’s notational system. The wavy marks or ‘writing’ describe a ‘time-based’ principle she named K-value. 2K corresponds to two upward strokes; 3K to three strokes and so on. Darboven’s practice can be seen as a performative gesture approximating machine-like labour. During a self-imposed, strictly regimented eight-hour day she generated line upon line and page upon page of handwritten script, recalling the first human computers who filled reams of paper with their longhand calculations charting the trajectories of comets, spacecraft and ballistic missiles.