1. The longest day of the year: June 21 marks the summer solstice, which is the longest day of the year in the Northern Hemisphere. In Arizona, residents can enjoy up to 14 hours of daylight on this date.

2. National Yoga Day: In 2015, the United Nations declared June 21 as International Yoga Day. To celebrate, many yoga studios and communities in Arizona organize events and classes to promote the physical, mental, and spiritual benefits of yoga.

3. Native American culture: June 21 is also significant for many Native American tribes in Arizona. On this date, the Hopi tribe celebrates the Soyal Festival, which marks the beginning of the new year and the return of the Kachina spirits.

4. Historical landmarks: Arizona has many historical landmarks that were founded or opened on June 21. For example, in 1908, the town of Winkelman was officially established in Pinal County, and in 1912, the Santa Fe Railroad expanded its line to reach Winslow, Arizona.

5. Summer activities: Arizona's warm weather during the summer months means that many outdoor activities become popular on June 21. From hiking and swimming to visiting water parks and attending outdoor concerts, there are many ways to enjoy the summer solstice in the Grand Canyon State.