To_date - Using Just Dd / Mm And Not Year

i am sure it may be wrong because it doesn't mention year however i have been told to get a list of all students who enrolled in MAY. and i have tried doing

select * from table where enrolDate > to_date('01-05','DD-MM') and enrolDate < to_date('31-05','DD-MM') and it doesnt work (says no rows selected when in fact there are some rows!

i can do it fine when using YEAR ie '01-05-2000','DD-MM-YYYY' another problem.

I am trying to do this:

Select to_char(to_date(01012008,DD-MM- YYYY),DAY) from dual;

and it is giving me the error however if i do this:

Select to_char(to_date(16012008,DD-MM-YYYY),DAY) from dual;