I have a message table schema like this (msg_id, msg_from_id, msg_to_id, msg_text, msg_time). ...and I'm thinking about the conversion of the message timestamp.
What's the better approach between the two?
The simple and correct solution is to set the database parameter timezone correctly for the client session:
SET timezone = 'Asia/Kolkata';
Then the database will render all timestamp with time zone correctly for that time zone. In short, PostgreSQL can do the time zone management for you.