From Wikipedia:

May 5th is National Cartoonist Day, a world-wide celebration of cartoonists and their work. The National Cartoonist Society declared the date in the 1990s to promote support for the cartooning industry, and to recognize the impact they have had on society. The establishment of the Day was ‘spearheaded by co-chairpersons Polly Keener and Ken Alvine of the National Cartoonists Day Committee.’