In the operator precedence table[1] table, AT TIME ZONE isn't explicitly listed out; that means it's to be interpreted in the "any other operator category".
However, it seems that the precedence of AT TIME ZONE is actually higher than that of the addition operator:
-- Fails with "function pg_catalog.timezone(unknown, interval) does not exist SELECT now() + INTERVAL '14 days' AT TIME ZONE 'UTC';
-- Works: SELECT (now() + INTERVAL '14 days') AT TIME ZONE 'UTC';
Note that missing parentheses for this were discussed in the context of pg_catalog.pg_get_viewdef[2].
Is there a missing line in the operator precedence table in the docs?