From the designer’s description:
For example at 3 o’clock the 3rd hour marking becomes dark and then a colored bar starts growing within the 3rd marking at every minute until the 59th minute. Then the 4 o’clock marking become fully dark and the same process continues. Even though it looks unique and has kind of ‘digital’ look and feel because of the growing bar, it uses exactly same mechanism as a normal clock.
We’ve got a time-lapse video that shows how the clock works after the jump. This looks like a concept clock, but we’ll be sure to update you if it heads for the production line.