On the 9th of June, the Hellenic Dipolieia/Bouphonia festival is observed.
The Dipolieia/Bouphonia is a festival which is dedicated to Zeus.
The clergy would ritualistically sacrifice an ox for the desecration of Zeus’s alter at the Acropolis. Afterwards the ox would be eaten during a feast as part of the festivities.
This is an auspicious time to make an offering to Zeus to recognize him as the king of the Gods.
Here is a prayer you can use to honour Zeus on this day:
“To the Son of Cronos, Most High
 I will sing of Zeus, chiefest among the gods and greatest, all-seeing, the lord of all,
the fulfiller who whispers words of wisdom to Themis as she sits leaning towards him.
Be gracious, all-seeing Son of Cronos, most excellent and great!”
The Homeric Hymns a Translation by Hugh G. Evelyn-White