Conversation so far:
who said you can't step into the same river twice
Heraclitus, a Greek philosopher born in 544 b.c. said, “No man ever steps in the same river twice, for it's not the same river and he's not the same man.”
what's the meaning of no man ever steps in the same river twice
The statement no man ever steps into the same river twice is an analogy for Heraclitus's belief that everything is constantly changing.

Question: when was the philosopher born
Self-contained rewrite: when was heraclitus born