PL/SQL :: How To Delete Records Checking Data And Time

I want to delete the records which are less than or equal to this date 

MIN(TRUNC(sale_week_date)-(1/(24*60*60)))  

For that I have created the following procedure.

 CREATE OR REPLACE PROCEDURE DELETE_DATA_WEEKISMIN_DATE DATE;SELECT MIN(TRUNC(sale_week_date)-(1/(24*60*60))) INTO MIN_DATE
FROM sales_week; DBMS_OUTPUT.PUT_LINE(MIN_DATE); 
DELETE FROM sales WHERE sale_date <= MIN_DATEAND sales_creation_date <= MIN_DATEAND sales_update_date <= MIN_DATE; END;

 If declare as MIN_DATE Date;

it's not taking time. If declare as MIN_DATE Timestamp; It is taking milli seconds also. 18-OCT-13 11.59.59.000000 PM SALE_DATE ,SALES_CREATION_DATE and SALES_UPDATE_DATE in this  format  18-OCT-2013 11.59.59 AM. How  to delete the records which are less than or equal to this date  MIN(TRUNC(sale_week_date)-(1/(24*60*60))) ..