You could run set time zone UTC; before your query:
set time zone UTC;
SELECT to_timestamp(field1, 'YYYY-MM-DD hh24:mi:ss')::timestamp without time zone at time zone 'Etc/UTC';
Does this solve your issue ?
You could run set time zone UTC; before your query:
set time zone UTC;
SELECT to_timestamp(field1, 'YYYY-MM-DD hh24:mi:ss')::timestamp without time zone at time zone 'Etc/UTC';
Does this solve your issue ?