Pop Music Chart Day is observed worldwide every January 4, celebrating the cultural influence of pop music and commemorating the release of the first-ever music chart by Billboard magazine in 1936. This unofficial holiday encourages people to listen to their favorite pop hits, create playlists of popular songs, and share them on social media. The origins of the holiday are unclear, but it marks the anniversary of the modern pop music charts, which rank recorded music based on criteria such as radio airplay, record sales, downloads, and streaming activity. Notably, the first music chart in the UK was introduced in 1952, inspired by Billboard's chart. Celebrations may include hosting music chart-themed parties or singing along to pop songs while driving. The Billboard Hot 100, introduced in 1958, remains the standard record chart in the American music industry.