SELECT
    FIRST_DAY(OF MONTH FROM CURRENT_DATE),
    LAST_DAY(OF MONTH FROM CURRENT_DATE),
    FIRST_DAY(OF YEAR FROM LOCALTIMESTAMP),
    LAST_DAY(OF YEAR FROM LOCALTIMESTAMP),
    FIRST_DAY(OF WEEK FROM DATE '2017-11-01'),
    LAST_DAY(OF WEEK FROM DATE '2017-11-01')
FROM rdb$database;