The Timor perpetual calendar was designed by Enzo Mari in 1967 for Italian manufacturer, Danese Milano. Believed to have been inspired by railway signs, it uses the Helvetica sans-serif typeface on a series of lithographed polyvinyl chloride (PVC) cards representing each day, week and month. These are fixed to a central point so that they can be easily flipped into place as appropriate. The body is made of green coloured injection moulded acrylonitrile butadiene styrene (ABS). The sleek, sculptural form is intended to be instinctive in use and will never become obsolete. It is still in production today, available in Italian, English, French and German language versions.