It's Commercial Broadcasting Day on April 21st。
In 1951 ()、 16 commercial broadcasters granted a preliminary broadcasting LicenseToProtect for the first time in Japan were。
In 1968 ()、 the National Association of Commercial Broadcasters of Japan established it as 「Broadcast Advertising Day」、 and in 1993 (Heisei5)、 it renamed to 「Private Broadcasting Day」 was。