October 1 is not a national holiday in the United States. However, there are several holidays and observances celebrated on this day. Here are some of the holidays and observances listed in the search results:

• International Coffee Day: A day to celebrate coffee and recognize the millions of people across the globe who work hard to create and serve it.

• National Homemade Cookies Day: A day to celebrate homemade cookies and the joy they bring to peoples lives.

• World Vegetarian Day: A day to promote the benefits of vegetarianism and raise awareness about the ethical, environmental, and health reasons for choosing a vegetarian lifestyle.

• Balloons Around the World Day: A day to celebrate the joy of balloons and the art of balloon twisting.

• Chinese National Day: A day to celebrate the founding of the Peoples Republic of China in 1949.

• Cyprus Independence Day: A day to celebrate the independence of Cyprus from British rule in 1960.

• Nigerian Independence Day: A day to celebrate Nigerias independence from British colonial rule in 1960.

• ROK Alliance Day: A day to commemorate the alliance treaty signing between the United States and the Republic of Korea.

• Teachers Day in Uzbekistan: A day to recognize and honor educators and teachers in Uzbekistan.

• World Sake Day: A day to celebrate sake, a traditional Japanese rice wine, and its cultural significance.

• National Fire Pup Day: A day to honor and recognize the brave and loyal dogs that serve as firefighters companions and mascots.

• National Pumpkin Spice Day: A day to celebrate the popular fall flavor of pumpkin spice.

• National Green City Day: A day to promote sustainable urban development and encourage people to take action to make their cities greener and more environmentally friendly.

• National Hair Day: A day to celebrate and appreciate the beauty and diversity of hair.

• International Day of Older Persons: A day to raise awareness about the issues and challenges faced by older people and to promote their rights and well-being.

Out of these holidays and observances, the most widely celebrated one is likely International Coffee Day, which is recognized by many countries around the world.