Conversation so far:
Why was Pink Floyd's Syd Barrett replaced?
Working with Syd Barrett eventually proved too difficult for the rest of the Pink Floyd band members.
What happened as a result of Syd Barrett being replaced by David Gilmour?
After Syd Barrett's departure, the burden of lyrical composition and creative direction fell mostly on Roger Waters

Question: When did Barrett get replaced?
Self-contained rewrite: When did Pink Floyd's Syd Barrett get replaced?