The default timestamp
type in Postgres is timestamp without time zone
.
To deal with this, employ the data type timestamp with time zone
.
Or run your database with the time zone set to UTC and use timestamp [without time zone]
.
Be aware that the time zone setting of the session is relevant to what Postgres actually returns for your queries.
This related answer provides all the details you might need:
Ignoring timezones altogether in Rails and PostgreSQL