Final answer:
Delphi became truly panhellenic around the 8th century BCE, a time marked by the end of the Greek Dark Ages, the documentation of Homeric epics, and the emergence of shared Hellenic cultural institutions.
Step-by-step explanation:
Delphi became truly panhellenic around the 8th century BCE. This period marks the end of the interlude of the Greek Dark Ages and coincides with the composition of the Homeric epics, the Iliad and the Odyssey, which are symbolically significant to Greek cultural unity.
The 8th century BCE is also known for the creation and spread of written works using the Greek alphabet. This era was foundational for the collective identity of the Greek poleis, laying the groundwork for what would become unified cultural practices and institutions that transcended individual city-states, such as the Panhellenic games and the Panhellenic sanctuaries, underscoring a shared Hellenic identity.