This amphictyony seems originally to have been instituted simply for the purpose of religious worship in the common sanctuary of Apollo Delios, the patron god (, theos patroos) of the Ionians, who was believed to have been born at Delos. The Delia, as appears from the Homeric Hymn to Apollo (147), had existed from very early times, and were celebrated every fourth year, possibly in the Athenian month of Hieros, or in Thargelion, to apply to Delos the Athenian calendar.
This amphictyony initially seemed to have been established solely for religious rituals in the shared temple of Apollo Delios, the revered deity (patron god) of the Ionians, who was believed to have originated from Delos. The Delia, as indicated by the Homeric Hymn to Apollo (147), had existed since ancient times and were observed every fourth year, possibly during the Athenian month of Hieros or Thargelion.