Cathode-Ray Tube Day is observed worldwide every December 20 to celebrate the invention of the cathode-ray tube (CRT), which was pivotal in the development of electronic television sets and computer displays. The holiday recognizes the contributions of various inventors, including William Crookes, who first named the rays in 1879, and Ferdinand Braun, who created the earliest version of the CRT in 1897. The first all-electronic television receiver using a CRT was demonstrated in 1926 by Kenjiro Takayanagi, while Philo Farnsworth is credited with the first Western version in 1927. The day also marks the anniversary of Vladimir Zworykin receiving his patent for the CRT in 1938. Celebrations may include learning about the history of CRTs, visiting technology museums with vintage displays, playing retro computer games, and sharing knowledge about the holiday on social media using hashtags like #CathodeRayTubeDay and #CRTDay.