A watch that can run for an entire year on a single full charge is how Citizen is choosing to celebrate 50 years of solar-powered watchmaking. 

But the Eco-Drive PHOTON is doing more than demonstrating how far the technology has come. 

Its unusual dial turns the physics of light into part of the watch's design, creating a timepiece that connects Citizen's engineering history with its next chapter.

Citizen's Eco-Drive PHOTON marks 50 years of solar watchmaking, with a movement that runs for 365 days on a full charge. Credit: Citizen Watch


The Japanese watchmaker unveiled the Eco-Drive PHOTON on March 19, 2026, marking the 50th anniversary of its first analogue light-powered watch, introduced in 1976. 

The anniversary collection consists of two limited-edition models, each restricted to 5,000 pieces worldwide. 

Both feature a new movement capable of operating for 365 days after a full charge, even without further exposure to light.

Two overlapping metal plates turn the PHOTON's dial into a tribute to the double-slit experiment, while concealing the solar technology beneath. Credit: Citizen Watch


That figure is particularly significant when viewed against the history of solar watches. 

Citizen's original light-powered timepiece, the Crystron Solar Cell, arrived during a period when the watch industry was undergoing major changes. 

Quartz technology was transforming timekeeping, but battery-powered watches introduced a practical inconvenience: their batteries needed regular replacement.

Fifty years after the 1976 Crystron Solar Cell, Citizen pushes light-powered watchmaking further with its new 365-day power reserve. Credit: Citizen Watch

Citizen had been exploring another possibility. 

In the early 1970s, amid a global energy crisis, its engineers began investigating sunlight as a cleaner 

and more convenient source of power. 

The objective was straightforward: develop a watch that could operate without depending on frequent battery changes.

The company produced its first prototype of a light-powered analogue quartz watch in 1974. 

Two years later, the Crystron Solar Cell became the world's first commercially released analogue light-powered watch. 

Its dial incorporated eight solar cells that collected light and converted it into electrical energy.

The technology worked, but early versions had limitations. 

Solar cells were less efficient than modern alternatives, meaning the watches needed considerable exposure to light to maintain their charge. 

Citizen spent the following decade improving both its solar cells and rechargeable batteries. 

By 1986, its watches could operate for approximately 200 hours on a single charge.

A more substantial development followed in 1995, when Citizen officially introduced the Eco-Drive name. 

The Eco-Drive Calibre 7878 placed its solar cell beneath the dial rather than displaying it prominently on the watch face. 

This allowed the watch to retain a more conventional appearance while still harvesting light.

The technology also benefited from improvements in rechargeable battery chemistry. 

With lithium-ion technology extending the available power reserve, some Eco-Drive watches could operate for up to 180 days in complete darkness.

Today, the Eco-Drive family covers everything from professional dive watches to GPS-equipped timepieces. 

Citizen has also developed exceptionally thin models, including an Eco-Drive watch measuring just 2.98mm thick. 

The new PHOTON continues that progression, although its most interesting feature is not necessarily the movement.

Its dial is inspired by the double-slit experiment, one of the most recognisable demonstrations in quantum physics. 

The experiment involves passing light through two narrow openings and observing the pattern produced when it reaches a detection surface. 

Depending on how the light is measured, the results reveal behaviour associated with both waves and particles.

Citizen has translated that scientific concept into a physical design. 

The PHOTON's dial uses two overlapping metal plates, each featuring a series of ripple-like slits. 

Beneath them sits a structural colour film, which becomes visible through the openings.

Structural colour is different from the conventional colours produced by paint or pigments. 

Instead of relying on coloured substances, it uses microscopic surface structures to reflect light in particular ways. 

The resulting colours can shift depending on how light strikes the material and the angle from which it is viewed.

On the PHOTON, this creates a layered appearance in which the reflected light produces changing hues across the dial. 

The arrangement also gives the watch a noticeable sense of depth, with the metal plates, openings 

and underlying film working together rather than presenting a flat surface.

The design is more than a decorative anniversary treatment. Light is simultaneously the subject of the dial 

and the energy source that keeps the watch running. Citizen has effectively made the technology behind 

Eco-Drive part of the visual identity of the product.

Powering the two models is the new Calibre E036 Eco-Drive movement. 

It offers a power reserve of 365 days when fully charged, meaning the watch can continue operating for an entire year without additional light exposure. 

Citizen specifies an accuracy of ±15 seconds per month.

The specifications also include a rounded octagonal case measuring 39.6mm across and 9.9mm thick. 

Both versions use dual spherical sapphire crystal with an anti-reflective coating, which reduces reflections 

and makes the dial easier to read. Water resistance is rated at 5 bar, while luminous hands and indices improve visibility in darker conditions.

Citizen has used its proprietary Super Titanium for the case and bracelet. 

The material combines the relatively low weight of titanium with a hardened surface designed to resist scratches. 

According to the company, it is at least five times harder than conventional stainless steel.

The two versions take noticeably different approaches to their appearance. 

The BJ6560-53W features a silver-coloured finish, with a yellow second hand providing a contrasting accent. 

Its case uses Duratect titanium carbide surface treatment.

The BJ6569-59X adopts a darker black-and-gold combination, complemented by a purple second hand. 

It uses Duratect DLC and amber-yellow finishes, giving it a more dramatic appearance. 

Both watches carry an engraved Eco-Drive 50th Anniversary logo and an individual limited-edition number on the case back. 

They will also arrive in specially designed presentation boxes that echo the slotted dial pattern.

The pricing reflects the distinction between the two editions. 

Citizen lists a projected price of US$1,000 for the BJ6560-53W and US$1,200 for the BJ6569-59X. 

Both are scheduled for release in autumn/winter 2026, with 5,000 examples of each model planned worldwide.

There is a certain symmetry in the PHOTON's arrival. 

The original Crystron Solar Cell emerged from an attempt to make watches less dependent on disposable batteries. 

Fifty years later, Citizen is presenting a technology that has evolved from a relatively simple arrangement of solar cells

into a sophisticated power system capable of sustaining a watch for 365 days on a full charge.

Finally....


The next question is how far that evolution can go. Solar cells, rechargeable storage 

and movement efficiency have all improved considerably since 1976, 

and the PHOTON shows that there is still room to explore how those components can be integrated into increasingly ambitious designs. 

Citizen's anniversary watch looks back at half a century of progress, 

but its more interesting proposition is what the next 50 years of harvesting light might make possible.

Sources: Citizen Watch, New Atlas.