Conversation so far:
What is a librettist?
A librettist is the writer of a libretto, text used in, or intended for, an extended musical work such as an opera, operetta, masque, oratorio, cantata or musical.
What notable piece did Jean-Philippe Rameau create ?
Rameau produced his most important comic opera, Platée in 1745.

Question: When did he create it ?
Self-contained rewrite: When did Jean-Philippe Rameau create it ?