This defintely confused me the first time I saw it. If you look carefully,you will see the Ink Calendar is composed all the days of a month (they’re white against a white wall). Basically,every day one of these numbers gets filled with the “Ink”from the container,to show you the date. The ink itself varies in color depending on what month it is (dark blue for December and greens for June and July). I am still trying to understand how it “resets”or knows which month it is,however,this isn’t just a fictional concept. Lucky for us (well not me),you can actually use it in the “Gradual”exhibit in Círculo de Bellas Artes in Madrid. (Found on Gizmodo)