The Dragon Boat Festival is a traditional holiday originating in China, occurring near the summer solstice. The festival now occurs on the 5th day of the 5th month of the traditional Chinese calendar, which is the source of the festival's alternative name, the Double Fifth Festival. The Chinese calendar is lunisolar, so the date of the festival varies from year to year on the Gregorian calendar. In 2017, it occurred on 29 May; in 2018, on 18 June; in 2019, on 7 June and, in 2020, it will on 25 June.

More Info: en.wikipedia.org