ZIP Code Day is celebrated every July 1 in the United States, honoring the numerical system that has significantly improved mail delivery efficiency across the country. This day encourages individuals to appreciate the role of ZIP codes in their daily lives and to recognize the logistics behind mail services. Common customs include sending handwritten letters or postcards to friends and family, ensuring to include the recipient's ZIP code. While the holiday does not typically feature widespread commercial deals, some businesses may offer promotions related to postal services, such as discounts on online postage or shipping. The day serves as a reminder of the importance of the postal system and the connections it fosters through mail. Joseph P. Nolan is often credited with the early development of the ZIP Code concept, which has transformed the national mail system.