oracle processing date

select sysdate from dual;  --get


the last last day
select last_day(add_months(sysdate,-1)) from dual;




select to_date(add_months(last_day(add_months(sysdate,-1))+1,-1)) from dual;


select trunc(sysdate), to_date(to_char(sysdate,'yyyy-mm-dd')||'23:59:59', 'YYYY-MM-DD HH24:MI:SS') from dual;


select trunc (sysdate), to_date(to_char(sysdate,'yyyy-mm-dd')||'00:00:01', 'YYYY-MM-DD HH24:MI:SS') from dual;


---Get the previous Last day of month select to_date
(to_char(
     (select last_day(add_months(sysdate,-1)) from dual)
   ,'yyyy-mm-dd')||'23:59:59', 'YYYY-MM-DD HH24 :MI:SS') from dual;
   
---Get the time of the first day of the previous month
select to_date(to_char(
  (select  to_date(add_months(last_day(add_months(sysdate,-1))+1,-1))  from dual)
,'yyyy-mm-dd')||'00:00:01', 'YYYY-MM-DD HH24:MI:SS')  from dual;