A thin crescent moon rotates to show it's position in the lunar cycle. This is one of the many faces of Disk Clock. Day Disk https://chrome.google.com/webstore/detail/ombigfjidloamaacoapfbanggkmekkhd Disk Clock https://chrome.google.com/webstore/detail/mgnkijdpagnigijnlnbofmjdpjjmhnpm