Default Display Format for Date Field in Oracle SQL Developer

i was running very simple query as given below

select invoice_num , invoice_amount*-1 , creation_date from ap_invoices_all where creation_date > to_date(:dt,'dd-mon-yyyy') and source = :source order by 3 , 2 desc;

Date was displayed in DD-MON-YY format. For a given date, second column i.e. invoice_amount was not displaying in right order. It made me think for a while and then i realized that creation date has time component too and that is why invoice amount is not in desired order. Truncating invoice date solved the problem.

This link http://www.zen-workshop.com/blog/v2/learning/default-date-field-display-format-in-oracle-sql-developer/ explains how to change default display format of date column in SQL Developer.