How to convert a unix time to PostgreSQL' Timstamp without timezome?
Here are a couple of approaches:

I've simplified your query, as you shouldn't need the TRUNC(), nor the CAST().

SELECT to_timestamp(1395036000) AT TIME ZONE 'UTC';

SELECT timestamp '1970-01-01 00:00:00' + interval '1395036000 second';


For reference, more information can be found at the following links:


First
query
Second
query