According to some pagan calendars, May 14 is listed as the Birthday of Apollo. However, according to the mythology, Apollo was born on the seventh day of the month Thargelion. Wikipedia goes on to say that this was according to Delian tradition, and that according to Delphian tradition, it was the seventh day of the month of Bysios. The seventh and twentieth, the days of the new and full moon, were also held sacred to him.
If the exact date is important you you, I’d suggest you take a look at the Wikipedia article on the Attic Calendar which gives the names of the months and their approximate times in the year. For the purposes of simplicity, I would suggest that the 7th day following either the New or Full Moon in May (May 17 in 2017) would fit the criteria and make for a fine day to celebrate the birth of the God of Light Apollo.
Who is Apollo? Here’s a brief profile:
Apollo is the son of Zeus and Leto. His twin sister is Artemis. He is the god of music, playing a golden lyre. The Archer, far shooting with a silver bow. The god of healing who taught man medicine. The god of light. The god of truth, who can not speak a lie.
One of Apollo’s more important daily tasks is to harness his chariot with four horses an drive the Sun across the sky. He is famous for his oracle at Delphi. People traveled to it from all over the Greek world to divine the future. His tree was the laurel. The crow his bird. The dolphin his animal.