Find number of days in any month modded by some day-of-month

days_of_month.sql

postgresql
----
select 31 % (SELECT
	DATE_PART(
		'days',
		DATE_TRUNC('month', now() :: DATE) + '1 MONTH' :: INTERVAL - '1 DAY' :: INTERVAL
	)
)::integer

redshift
---
In addition to finding the number of days in a month, it mods a number against that.

select (14 % (
SELECT to_number(
	date_part(
		days,
		dateadd(
			DAY,
			- 1,
			dateadd(
				MONTH,
				1,
				DATE_TRUNC('month', getdate())
			)
		)
	), '99')
)) = 13