Radio Day, observed in the Philippines every May 8, commemorates the establishment of DZRB-AM, the country's oldest operational radio station. The history of radio in the Philippines began in the early 1920s, with the first broadcast attributed to Mrs. Redgrave in 1922. The first radio station, KZKZ, was founded that same year by Henry Herman Sr., but it ceased operations after a merger in 1925. DZRB, originally established as KZSO in 1933, has undergone several name changes and ownership transitions, particularly during the martial law era under Ferdinand Marcos. Today, the Philippines boasts between 1,200 and 1,500 radio stations, primarily broadcasting in AM and FM bands, with a mix of commercial, government-owned, and religious programming. Radio broadcasting is regulated by the National Telecommunications Commission, which assigns unique call signs to broadcasters.