I am confused now.

As I have learned, Visak Day is the full moon of the 6th lunar month- the day of Birth, Enlightenment and Death of the Buddha. The First Teaching was on the full moon of the 8th lunar month after the Enlightenment Visak -- and on the same day emerged the first arahat and first disciple (โกณฑัญญะ) -- and later when other 4 members of the '5-vaggiya' joined the order the three gems (Buddha, Dhamma, and Sangha) was complete for the first time.

There was a story that on His way to see the vaggiya, He met a young brahmin who praised His serene and savvy appearance and asked who was His Teacher. The Buddha replied that He had learned the true Dhamma by Himself. He had no teacher. The young brahmin shoock his head and walked away without proper courtesy. [We can perhaps say now that young Brahmin was the Buddha's teacher on Preaching. The buddha never started His teaching with self promotion again.]

Correct me if I am wrong. But the Moon is still bright and beautiful after the Visak and the Buddha's universal Dhamma still clear and perfect in our minds, let us say "Thank You Buddha!". ;-)