Last_day function for hijrah date (very important please reply as soon as possible)

Dear All,
I want to get the last day of a Hijrah date, after that I want to see the corresponding Gregorian date.
I am not getting the right answer could you please help me on this.
pls see the following example
 


select
to_date (to_char(sysdate,'dd mm rrrr','nls_calendar=''English Hijrah'''), 'dd mm rrrr') hijrah,
last_day (to_date(to_char(sysdate,'dd mm rrrr','nls_calendar=''English Hijrah'''), 'dd mm rrrr')) lday_hijrah,
last_day(to_date(to_char(sysdate,'dd mm rrrr','nls_calendar=''English Hijrah'''), 'dd mm rrrr')) lday_hijrah,
last_day(to_date(to_char(sysdate,'dd mm rrrr','nls_calendar=''gregorian'''), 'dd mm rrrr')) lday_greg