Citizen 30th Anniversary Edition | Eco-Drive | Atomic Timekeeping with Moonphase

A world first in horological innovation, the Tsuki-yomi A-T brings together moonphase functionality and atomic timekeeping in a design that celebrates Citizen’s 30-year legacy of breakthrough technology. This refined timepiece offers exceptional performance with a celestial touch.

Key Features

Moon-Inspired Design

• 43mm Super Titanium™ case with sharp, faceted edges for a sophisticated silhouette

• Deep green dial with black and silver-tone accents, inspired by the moon’s surface

• Moonphase window at 6 o’clock for a poetic yet functional complication

• Durable sapphire crystal with superior scratch resistance

Advanced Technology

• Caliber H874: Eco-Drive movement powered by light — no battery changes ever

• Atomic timekeeping: automatic time correction via radio signals for global precision

• World time in 24 time zones, perfect for international travelers

• Perpetual calendar with day-date functionality for hassle-free accuracy

Durability & Comfort

• WR100/10 bar (333ft) water resistance — ideal for daily wear, swimming, or snorkeling

• Constructed from Super Titanium™, 5x harder and 40% lighter than stainless steel

• Fold-over clasp with push buttons for a secure and comfortable fit

• Lug width: 22mm

The Citizen Tsuki-yomi A-T BY1010-57X merges technical mastery and elegant design in a timepiece that tracks both terrestrial and celestial rhythms. Featuring the world’s first moonphase + atomic timekeeping combination, this 30th Anniversary edition redefines what a modern dress watch can be — intelligent, precise, and cosmically inspired.