Examples of LAST_DAY
select
last_day(of month from current_date),
last_day(of year from current_timestamp),
last_day(of week from date '2017-11-01'),
last_day(of quarter from date '2017-11-01')
from rdb$database;
LAST_DAY
select
last_day(of month from current_date),
last_day(of year from current_timestamp),
last_day(of week from date '2017-11-01'),
last_day(of quarter from date '2017-11-01')
from rdb$database;