Time Zone offsets in the DB

When you need a timezone offset in the database use

select utc_offset from pg_timezone_names where name = 'Asia/Hong_Kong';

But in this case utc_offset is an interval and maybe you want an integer

select '1 hour'::interval::integer;   -- << THROWS ERROR

Throws an error cannot cast type interval to integer

But you can extract the hour from an interval

select extract(hour from utc_offset) from pg_timezone_names where name = 'Asia/Hong_Kong';

-[ RECORD 1 ]
date_part | 8

This operation can be unexpectedly expensive to run (100ms) so be careful where you run it or maybe put this rarely changing information into a materialized view.