Here is an interesting calendar design from Spanish designer Oscar Diaz, the Ink Calendar.
At the start of each month a bottle of ink is placed on the calendar, and the ink slowly penetrates the calendar throughout the month to display the date.
Ink Calendar make use of 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.
This certainly is an interesting design, the Ink Calendar is being exhibited at the Circulo de Bellas Artes in Madrid.