Kensington Watches
Citizen 'Tsuki-Yomi' Radio-Controlled Moon Phase 43mm Mens Watch

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Citizen

Citizen 'Tsuki-Yomi' Radio-Controlled Moon Phase 43mm Mens Watch

Ref. BY1010-57H

Among our 95 Citizen watchesThis watch£699
Premium

Sits in Citizen’s upper tier here — more premium than three quarters of the Citizen watches we list, which start at £139.

Price range £139 to £895 across 95 Citizen watches in stock.

The grey dial carries a textured pattern of the moon's surface, framed by a black outer ring. The moon phase display sits at six o'clock, automatically adjusted each day using Citizen's Luna Program, which calculates lunar position from multi-band radio signals — making this the first light-powered watch to feature a fully analogue radio-controlled moon phase. A day sub-dial and date aperture at four o'clock complete the layout, with luminous hands and baton indices. The 43mm case and bracelet are both built from Super Titanium, keeping weight low on the wrist. A sapphire crystal sits above the dial, and the fold-over push-button clasp secures the bracelet. The solar Eco-Drive movement offers a six-month power reserve and covers 24 world time zones, with the perpetual calendar adjusting automatically for month lengths and leap years. Water resistance stands at 100 metres.

Reference
BY1010-57H
Brand
Citizen
Case size
43mm
Lug width
22mm
Case material
Titanium
Case shape
Round
Dial
Grey
Crystal
Sapphire
Movement
Solar
Functions
Date, Moonphase, World time, Perpetual calendar, Solar powered, Radio controlled
Water resistance
100m
Bracelet / strap
Titanium bracelet
Strap colour
Silver
Clasp
Folding clasp
Lume
Luminous
Retailer
Goldsmiths
Learn more about Citizen

The Shokosha Watch Research Institute began in Tokyo in 1918, and the Citizen name was given to its first pocket watch in 1924 by the then mayor of Tokyo, Shinpei Goto, who wanted a watch that would be available to ordinary citizens rather than only the wealthy. The company formally took the name in 1930.

That founding intention has held. Citizen is the largest watch manufacturer in the world by volume and is fully vertically integrated, making its own movements, cases, and electronic components.

Its most significant technology is Eco-Drive, introduced in 1976 and refined over decades. A photovoltaic cell beneath the dial converts any light — including indoor light — into stored energy, so the watch never needs a battery change. Citizen has sold well over a hundred million Eco-Drive watches, and the environmental argument is substantial: hundreds of millions of cells not discarded.

The company also produced the first analogue quartz watch with a titanium case in 1970, the first professional dive watch with an electronic depth sensor, and the Caliber 0100, an Eco-Drive movement accurate to within one second a year — the most accurate independent watch movement ever put into production.

Citizen owns Bulova, Frederique Constant, Alpina, and the movement manufacturer Miyota, whose calibres power a large share of the affordable mechanical watch market worldwide.

1918
The Shokosha Watch Research Institute is founded.
1924
The Citizen name is given to its first pocket watch.
1976
Eco-Drive light-powered technology is introduced.
2018
The Caliber 0100 achieves accuracy of one second a year.

All Citizen watches

Also in 4 collections

This watch appears in Back in Stock (3,616), Grey Dial Watches (247), Solar & Kinetic Watches (225) and Titanium Watches (180).

Manufacturer’s guarantee

What the specifications mean

Strengths

  • 100m water resistance covers swimming and watersports
  • Sapphire crystal, which resists scratching
  • Luminous hands and markers for low light
  • Second time zone for travelling
  • One of Citizen's more premium watches

Worth knowing

  • 43mm sits at the larger end
Best forSwimmingTravelEveryday wear
Less suited toSmall wrists

Citizen 'Tsuki-Yomi' Radio-Controlled Moon Phase alternatives

Watches from other brands at a similar price, style and size, so you can see what else your budget can buy.

'Tsuki-Yomi' Radio-Controlled Moon Phase 43mm Mens Watch compared with 2 alternatives from other brands
SpecificationThis watch'Tsuki-Yomi' Radio-Controlled Moon Phase 43mm Mens WatchBY1010-57HSeikoProspex SFJ009P1 Speedtimer 110th Wristmaking Anniversary Watch - Limited Edition - W25439SFJ009P1GarminEpix (Gen 2) Carrera White 47mm Smart Watch010-02582-21
Price£699£665£630
Case size43mm42mm47mm
Water resistance100m100m100m
MovementSolarSolarSolar
StrapTitanium braceletStainless steel braceletSilicone strap
This watchClosely matched
  • Wears larger

Your new watch

Frequently asked questions, and things you should know about this watch

Can I swim with it?

Yes. At 100m it is rated for swimming and snorkelling, though not for diving.

Water resistance explained

Will the glass scratch?

Unlikely. Sapphire is second only to diamond in hardness and shrugs off everyday marking.

Sapphire, mineral and acrylic compared

Does it need a battery?

No. It charges from light, and the cell behind that is designed to last a decade or more.

Quartz, automatic and solar compared

What size strap does it take?

22mm. Any strap of that width will fit, and on most modern watches quick-release bars make the swap a two-minute job with no tools.

Is it a men's or women's watch?

Listed as men's.

Cheapest place to buy

Goldsmiths is the only UK retailer we track stocking this reference, so there is nothing to compare it against today.

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