Demonstration of OVERLAPS keyword vs checking date range with `>=` and `<=`

overlaps.sql

SELECT
  t1.*,
  (start_date, end_date) overlaps (range_start, range_end) as overlaps_func,
  (start_date <= range_end) AND (end_date >= range_start) as overlap_bool
FROM generate_series('2016-12-01'::date, '2017-03-10'::date, '1 day'::interval) as gs(date)
JOIN LATERAL (
  SELECT
    '2017-01-01'::date start_date,
    '2017-01-15'::date end_date,
    (gs.date::date - '30 day'::interval)::date range_start,
    gs.date::date range_end
) AS t1 ON true
ORDER BY 1;