Holy Moly! What a great idea. Spanish Designer Oscar Diaz designed a calendar which will display the date slowly by absorbing ink from a little bottle, which is also labeled with the current month. So every month a new sheet of paper will display the current date by the capillary action of ink spreading across paper. And the colors which are creeping across the paper are related to the way we see each month, green for spring, dark blue in winter.. Amazing!

His despriction:

“Ink Calendar make use the timed pace of the ink spreading on the paper to indicate time.
The ink is absorbed slowly, and the numbers in the calendar are “printed” daily. One a day, they are filled with ink until the end of the month. A calendar self-updated, which enhances the perception of time passing and not only signaling it.
The ink colors are based on a spectrum, which relate to a “color temperature scale”, each month having a color related to our perception of the whether on that month. The colors range from dark blue in December to, three shades of green in spring or oranges, red in the summer.

The scale for measuring the “color temperature” that I have used is a standard called ‘D65’ and corresponds roughly to a midday sun in Western / Northern Europe.
The “Ink Calendar” was developed for “Gradual “, an exhibition featuring works, which were evolving during the exhibition time at the London Design Festival 2007.
Production: Self-production.
Specs: Ink on paper, various dimensions.
Exhibitions: “Gradual” 5, Crownwell Place, London Design Festival, 2007.”

I wish there would be a fast motion video, which visualises the effect, by recording the calendar next to a clock! (found via Trend.Land)