November 1 is All Saints Day, a Christian observance held to honor all the saints, known and unknown. It is a national holiday in Mexico and many South American countries, where it is celebrated as the first day of the Day of the Dead (Dia de los Muertos), a two-day celebration honoring both deceased children and adults. In the United States, November 1 is also National Authors Day, National Cook For Your Pets Day, National Vinegar Day, and World Vegan Day, among others.