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.
The amphictyony initially appeared to be a simple arrangement for religious ceremonies in the common temple of Apollo Delios, the revered god of the Ionians, who was thought to have been born on Delos. The Delia, as revealed by the Homeric Hymn to Apollo (147), had existed since ancient times and were celebrated every four years, possibly during the Athenian month of Hieros or Thargelion.