Ink Calendar is a cleverly designed prototype of a self-advancing calendar by London-based artist Oscar Diaz. The basic idea behind the inventive day tracker is that a vile of ink is absorbed by a trail of paper cut into sequential numeric values–like a row on a calendar. What’s especially impressive is that the season-specific color of ink slowly soaks each number within a day’s time, allowing one to tell what day it is by how far the ink has made it on the calendar. Furthermore, this gradual progression across each day’s double-digit representation provides an awareness of time’s passage, especially on a daily scale. By the end of the month, the calendar’s numbers are designed to be fully soaked in color.