how to alter date format?

I enter the date value in this format.
oracle gives me
 ORA-01843: not a valid month error.
NOTE:(you can better understand the question in the pictures.
Please see the pictures.
but
I enter the date value in this format.
Oracle is running.
)
I want to change the date format.
I don't want to use this date (13.jun.2014),
 I want to use this date = (13.06.2014),
how can I do this?

Result of query 'select sysdate from dual'

17/09/2019 17:46:00

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