Korean designer Jeong Yong created this perpetual table calendar that’s made of three differently-sized rings.

The biggest ring represents the days – the 31 units during which the sun rises and sets. The middle ring, for the months, represents the moon’s orbit around the Earth. And, finally, the smallest ring, with seven units, represents the days of the week, or as the designer says “the people who created the seven days of the week.” Held together with strong magnets, you can join up the month, day and week to keep you on track, but with the added bonus of a cool, desktop sculpture.