International Day of Light 2027 is on Sunday

About International Day of Light

The International Day of Light highlights how much modern life depends on light: fiber-optic internet, medical imaging and laser surgery, solar power, astronomy, photography and lighting design. It also covers the cultural side of light, from art to architecture, and questions of access, such as the many people who still lack reliable, affordable lighting at home.

May 16 marks the anniversary of the first successful operation of a laser, achieved in 1960 by the American physicist and engineer Theodore Maiman. The organizers chose the laser as an example of a discovery that began in a research lab and went on to change communications, health care and industry, while stressing that the day is about far more than lasers.

The day grew out of the International Year of Light and Light-based Technologies in 2015, a UN observance led by UNESCO. Partners from that year wanted a lasting follow-up. Ghana, Mexico, New Zealand and the Russian Federation proposed an annual day, which UNESCO's Executive Board backed in September 2016. The UNESCO General Conference proclaimed it at its 39th session on November 7, 2017, and the first International Day of Light was held on May 16, 2018, with a flagship event at UNESCO headquarters in Paris.

The day is coordinated through UNESCO's International Basic Science Programme with a steering committee of scientific and industry partners, and events are organized locally by universities, research centers, museums and schools. UNESCO's 2026 observance focused on how large light-based research facilities support scientific development and innovation.

Sources: UNESCO: International Day of Light, International Day of Light: Background, International Day of Light: Why May 16th?, ICTP: UNESCO proclaims International Day of Light (November 2017). How we check dates.

How to mark International Day of Light

• Join a public lecture, open lab or online webinar listed by a university physics department, observatory or synchrotron facility.
• Try a simple optics experiment at home or in class, such as splitting sunlight into a spectrum with a glass of water or a CD.
• Look up how fiber-optic cables carry internet data as pulses of light, and trace how your own connection reaches you.
• Check your outdoor lights and switch to shielded, warm-colored fixtures that cut glare and light pollution.
• Visit a museum or gallery exhibit that uses light as an artistic medium, or photograph how light changes in one place through the day.

International Day of Light dates