Citizen Watch Tsuki Yomi Radio Controlled Moonphase BY1010-57L. Introducing the Citizen 'Tsuki-yomi' Radio-Controlled Moon Phase - the worlds first light-powered radio-controlled moon phase movement. To celebrate the 30th anniversary of the first CITIZEN radio-controlled watch we are debuting the worlds first fully analogue moon phase function for light-powered watches. The Tsuki-yomi collection (directly translating to reading the moon) features a new radio-controlled Eco-Drive Cal. H874 movement that provides 15 seconds accuracy per month, revolutionary proprietary Super Titanium? material and artfully crafted moon pattern dials. Based on a unique mathematical formula developed by CITIZEN called Luna Program, the watch calculates the phase of the moon each day from signals received from multi-band radio transmitters. The phase of the moon at the six oclock position is then automatically adjusted and displayed. With a striking blue pattern of the moons surface on the dial paired with a black outer ring, and date display at the 4 oclock position. Sustainably powered by any light, including moon light, with our proprietary Eco-Drive technology, this timepiece never needs a battery.