At its 39th session in 2017, UNESCO's General Conference proclaimed 16 May as the International Day of Light, first observed in 2018. The date marks the anniversary of the first successful operation of the laser in 1960 by American physicist and engineer Theodore Maiman, a breakthrough that reshaped modern science and technology. The idea for a permanent annual day built on the success of the International Year of Light and Light-based Technologies, celebrated by UNESCO in 2015 with an initiative backed by Ghana, Mexico, New Zealand, Russia, and more than 27 other countries. The day promotes global understanding of light's role across many fields, from physics and medicine to communications, art, and cultural heritage. Universities and scientific and cultural institutions worldwide mark the occasion with public science lectures, art exhibitions inspired by light, educational activities for children on the physics of light, and discussions on how light-based technologies contribute to sustainable development goals such as clean energy and communications.