When did Aristotle's academy open?

Answer 1

in 335 BC

In about 335 BCE, Alexander departed for his Asiatic campaign, and Aristotle, who had served as an informal adviser (more or less) since Alexander ascended the Macedonian throne, returned to Athens and opened his own school of philosophy. He may, as Aulus Gellius says, have conducted a school of rhetoric during his former residence in Athens; but now, following Plato's example, he gave regular instruction in philosophy in a gymnasium dedicated to Apollo Lyceios, from which his school has come to be known as the Lyceum. (It was also called the Peripatetic School because Aristotle preferred to discuss problems of philosophy with his pupils while walking up and down -- peripateo -- the shaded walks -- peripatoi -- around the gymnasium.)