current date minus 30 days in postgresql code example

Example 1: today minus 15 days postgresql

--yesterday
SELECT NOW() - INTERVAL '1 DAY';

--Unrelated to the question, but PostgreSQL also supports some shortcuts:
SELECT 'yesterday'::TIMESTAMP, 'tomorrow'::TIMESTAMP, 'allballs'::TIME;

Example 2: current date in postgresql minus 1 day

CURRENT_DATE-INTERVAL '1 DAY'