It was designed by Spanish designer Oscar Diaz. The date is displayed using the capillary action of ink spreading across paper. Each month, a bottle of coloured ink spreads across a sheet of paper embossed with numbers, colouring them in as it goes.

Ink Calendar is being exhibited at an exhibition called Sueños de un Grifo - Diseño con Alma de Aguaat the Círculo de Bellas Artes in Madrid 17 July to 11 October 2009.