SQL

oracle first day of last year

-- Oracle: First day of previous year
SELECT trunc(add_months(sysdate, -12), 'YEAR') FROM DUAL;

oracle first and last day of previous month

select add_months(trunc(sysdate,'mm'),-1), last_day(add_months(trunc(sysdate,'mm'),-1)) from dual 

oracle last day of month

-- Last day of current month
SELECT trim(to_date(last_day(sysdate), 'DD/MM/YYYY')) AS LASTDAY FROM DUAL;