Feature-heavy watches can create their own problem. World time, calendars, radio synchronization, and moonphase displays sound useful individually, but combine too many complications and you can end up with a watch that demands more attention instead of less.
Price: $716
Where to Buy: Citizen
The Citizen Tsuki-yomi A-T BY1018-55X takes a different approach. It combines radio-controlled timekeeping, Eco-Drive power, world time, a perpetual calendar, day and date displays, and a calculated moonphase in a watch designed to minimize routine adjustments.
At the time of writing, Citizen lists this red-dial model for $716, down from $895. It has a 43mm Super Titanium case, a matching bracelet, sapphire crystal, 100-meter water resistance, and Citizen’s H874 Eco-Drive movement.
That combination makes the Tsuki-yomi worth a look if you enjoy watch complications but not the upkeep that can come with them.
Radio control reduces time corrections
The H874 can receive time signals from stations in Japan, the United States, Germany, and China. It attempts automatic reception once a day, and you can start reception manually. When it receives a signal successfully, it adjusts the time, calendar, and moonphase indication.
The limitation is location. Reception depends on being within range of a transmitting station and on conditions such as buildings, terrain, weather, and electrical interference. This is not a watch that can synchronize by radio everywhere you travel.
It still keeps time without a signal. Citizen rates the H874 for an average accuracy of ±15 seconds per month when it runs without radio reception. Think of synchronization as an automatic correction feature, not a requirement for the watch to work.
Eco-Drive cuts down on battery changes
Citizen’s Eco-Drive system converts light into energy stored in a rechargeable cell. It eliminates routine disposable-battery replacements, though the watch does contain a rechargeable cell and needs enough light to stay charged.
Citizen specifies approximately six months of operation on a full charge without additional light. Its power-save function can extend that duration when the watch is kept in the dark, but it does not receive time signals while power save is active.
Paired with radio control, Eco-Drive supports the watch’s central appeal: fewer routine tasks for its owner. You do not need to keep an automatic movement wound, replace a conventional battery periodically, or correct the time by hand when signal reception is available.
The moonphase calculates, rather than detects
The display at 6 o’clock gives the Tsuki-yomi its name and its most distinctive feature. Citizen calls it the world’s first watch to combine a moonphase display with the company’s atomic timekeeping technology. That is Citizen’s claim, not an independently verified industry first.
The watch does not detect the Moon’s position. Instead, the H874 calculates the moonphase from its time and date. You can switch the display between Northern and Southern Hemisphere views and calibrate it by up to two days if the indication differs from what you see.
Citizen describes the display as a reference for the moonphase, not a detailed depiction of the Moon’s appearance. Even with that qualification, it is more than a decorative moon on the dial: it is an indication the watch calculates and updates.
The calendar fits the low-maintenance theme
The Tsuki-yomi also offers world time across 24 selectable time zones, plus day and date displays. Its perpetual calendar accounts for different month lengths and leap years without monthly correction through February 28, 2100.
That matters in a watch designed to require less attention. There would be little point in light-powered, radio-controlled timekeeping if you still had to fix the date after every short month.
The world-time feature lets you select a time-zone offset; it does not display the time in 24 cities at once. You must select the appropriate time zone yourself, whether or not radio reception is available. Outside supported reception areas, summer-time changes may also require manual adjustment.
Titanium helps with the 43mm size
The case measures 43mm across, which remains an important consideration if you prefer smaller watches. Titanium can reduce weight, but it cannot make a 43mm watch wear like a compact one.
Citizen lists the BY1018-55X at 105 grams with its Super Titanium bracelet. The bracelet has a fold-over clasp with push buttons, while the case has a 22mm lug width. Citizen’s Super Titanium designation refers to titanium treated with the company’s surface-hardening technology.
We have not worn this model long-term, so its durability on a particular wrist is not something we can judge here. The stated weight and dimensions, however, give you useful starting points when comparing it with your current watch.
Sapphire and water resistance add versatility
A sapphire crystal protects the dial, and Citizen rates the watch to 100 meters, or 10 bar, of water resistance. Citizen specifically lists swimming, showering, and snorkeling among the activities covered by that rating.
That makes the Tsuki-yomi more versatile than its intricate-looking dial might suggest. As with any water-resistant watch, keep the crown secured and do not operate the crown or buttons while the watch is wet.
Who is the Tsuki-yomi A-T for?
The BY1018-55X makes the most sense for someone who wants a feature-rich watch without making watch maintenance a hobby. Radio synchronization can correct the time where reception is available. Eco-Drive avoids routine disposable-battery changes, and the perpetual calendar reduces date adjustments. The calculated moonphase is not essential, but it gives the watch its character.
Its size is the clearest tradeoff. The 43mm case will be too large for some wrists and tastes, regardless of its titanium construction. Radio reception also depends on where you live or travel.
Price: $716
Where to Buy: Citizen
If you want the hands-on ritual of setting a mechanical moonphase, this Citizen offers a different experience. If you would rather have a moonphase watch that handles much of its own upkeep, the Tsuki-yomi A-T makes an unusually long feature list feel purposeful.
